That 4 month mark really does come on suddenly (not to scare anyone). Is it me?

Training context. I've worked with him each and every day from 8 weeks old. Currently unemployed so had all my time to put toward training. I've trained rescues in the past but all were over the 'teen' threshold. I spend atleast 3 hours daily training, through positive reinforcement split up through games and random situations we'd encounter.

Our boy turned 4 months around a week ago, and was given the all go by vets for outdoor time a few days beforehand. God. A switch was so suddenly flicked the DAY 4 months came around I'm not even joking. It's been especially hard for me as I've been his main trainer. Watching our progress bar go back to zero has been a tough one for me to swallow, we were making such amazing progress and I began to see a glimmer of the adult dog he could become. Not anymore lol...

Attitude. It has begun. Let me say he was already quite standoffish as a young puppy but all behaviours were done without intent. Now he is older and intentionally pushing boundaries and displaying problem behaviours out of no where just to get a reaction. Lawd.

One very frustrating one that he started up a few days ago, jumping and biting the lead while going toilet. He gets himself so worked up and excited over the lead (to the point he'll sprint around so fast it's as if he'll take off) and often when he realises the lead is stopping his full potential, will begin nipping at you! I've put in countless hours of lead work, taking our time getting used to walking around indoors, in the corridor and outside. All that gone in a single week. Of course straight back inside and to his pen. What really gets me is he will need to go number 2 so so badly, but clearly forgets when he gets in these worked up states. I often have to do multiple trips up and down with him for hours (We live on the 3rd floor of an apartment complex, upside is I keep fit). These trips make me upset as neither of us are having a good time, but I can't exactly let him continue this behaviour through reinforcement with attention. So it's down without talking, huge reward if he does go and attention once again, if he hasn't gone then take him back to his pen in silence and back down again once he inevitably voices he needs to go. Often I've found he acts out when getting tired, but it can get triggered from anything he slightly disagrees with now.

I don't even want to mention the attention barking. The one thing I wanted to be sure he knew from day 1 was settle, and he knows it very very well. Now he actively ignores it, but what puzzles me is he knows he doesn't get anything from it. Taking a step back in his self settling, I sit on the sofa by his play pen. He has exercised, drank, eaten and had time with me. The moment he realises I'm now relaxing alone, barking. I get up and leave, he cries and I tell him to settle from outside the room to which he goes and settles on his bed. I have communicated so clearly what behaviours I want from him, he knows them. I come back and sit on the sofa returning my presence as a reward. I've done this for so long, and before 4 months his progress was amazing. He would only bark for toilet or if he really did need something, now he does it as a tantrum even though he h a t e s the repercussions (me leaving the room).

He has become more nervous which was expected. Before the 4 month mark he was more than happy to take the short 5 minute walk to our nearby park, extremely quiet and mainly open fields. Now I've made the decision to take him back to watching the front of our complex and doing outdoor training out the back of our complex. Every little thing gets him (of course puppy so expected). Not to jinx but I'm thankful in a sense he is more fearful and tends to just sit and watch when distracted rather than run after whatever catches his eye. I worked with him from 8 weeks old observing different environments and practicing very basic 'at me'. Having the redo all of this with a puppy who will now very randomly test boundaries is like a ticking time bomb. All I'll say is make sure you go at the pace of your puppy. When I realised he could no longer easily look at me while we were simply sitting on the park field I made us both take a huge step back. Now we're using the back of our complex again I'm so glad I did. Over the week he has struggled more and more with basics you'd expect to be second nature at this point, all natural for 4 month mark onward but very discouraging again. The back of our complex is a gated off car park, with hardly any traffic of people or cars during the day, it's completely surrounded by other apartments and houses, basically no distractions and yet he will find the single dry leaf in that tiny area and be unable to refocus.

Tonight we have our first puppy class. I'm quite confident with training basics so I bought the course more for access to a controlled distracting environment. I can't help but be nervous however. The worry tonight will expose all his problem behaviours while other owners sit calmly with their pups has me sweating. He was very food driven when it came to liver, chicken ect. but the 4 month mark seems to have changed him a lot. He isn't exactly driven in the way you'd see a collie pup or GSD pup, wanting to work for the reward, it's more so like bribery. Never was he like this and it will be good to have a chat to professionals tonight. Is it a me problem or is it just hormones beginning to change my little boy?

Anyone reading this with a pup under 4 months, don't be scared but I will say don't underestimate the ways in which your pup can suddenly change. I remember reading stories just like mine a few weeks ago and having a chuckle. No way my boy could regress THAT much! ... I was wrong.

Edit - I should've put in more explanation but the '3 hours of training' is 3 hours split into tiny periods throughout the entire day. These sessions have only been reinforcing sessions for weeks now, many game based and very relaxed. Reinforcing things such as picking to come to me instead of an item on the ground while free roaming, settling or simply playing fetch. I've been following the 1 hour up, 2 hours down which works very well.

I believe any interactions or situations your pup is placed in the be mini training sessions. I grouped most daily interactions into 3 hours but that was only an estimate, somedays its more or less. Thank you for being worried though! I'd be quite concerned if someone was training their pup strictly for hours straight too haha.