Tolerance ?

Using thc oil for couple weeks,there is no more head high just a little stoned feeling.Is it possible it's a tolerance thing?has my oil turned bad/due to heat exposure? I dono I didn't think I would be in this position already.Was only using the doctors recommended dosage and started of low and slow for first couple weeks.I just want to be head high again as it seems it's takes my mind of the pain.Any thoughts or sugge Would be appreciated.