What will 150 mg of diphenhydramine do for me?

Idk if I’m gunna get deleted if I say my age normal. I’m 51. Iykyk. So basically I am a very unwell person, im chronically ill and life just sucks rn. I need something to take away the pain, and last time I took too much of it my pain went away for awhile. I had mild hallucinations but overall I was fine, other than cotton mouth and stuff. What will happen if I take 150 mg? I’m in a lot of pain and just need it to stop. I’m pretty sure when I accidentally took too much it was around that amount, but I’m scared. I’m 5’4 140 lbs. female. All google will tell me is not to do it, or stuff abt overdose but from my understanding I wouldn’t be taking enough to OD, right? Just a high? Ik I’ll hallucinate and be rlly tired, ik what fatigue and drug induced drowsiness feels like, im not worried about that. And how long will it take to wear off? I have school tmrw and don’t wanna be like hallucinating too intensely there. Any advice or just info on experiences? Anything is appreciated.