Why does weed make me anxious after being a stoner for 3 years

I am so incredibly sad that weed makes me tweak out now. I used to smoke 24/7, driving, working, drawing, you name it. Smoked flower the moment I woke up and the moment I went to sleep. I stopped for like 3 weeks because I was training for a new job(that was hard to put it down) and then when I tried it again it felt so so incredibly bad. Feels like hell and gives me so much anxiety. Started doing worse and worse drugs to cope w life bc weed suddenly stopped feeling good. Tried countless times to use weed in tiny amounts and it just feels like HELL. Now I’m stuck on harder drugs yet weed makes me freak out. Can anyone explain this??? I smoked weed heavily for like 4 years it was my everything. wtf happened. Been trying to find explanation but to no avail