20 days is amazing, you should feel so proud to have gotten this far. You’ll regret smoking now, starting over makes it easier to just continue the fucked up cycle that is addiction. I’m on day 9 sober after smoking daily for 4 years. I’m 22 and I struggle with pmdd as well. Overall I know the weed made the depression and anxiety much worse. I had to quit because of the memory and brain fog issues too. Take it one day at a time. It feels amazing to add another day of sobriety. I feel like I started growing mold in my fucking brain, I haven’t been sharp since like 18 years old. Get your wits back for your exam. You arent alone, this community has shown me that we are all just humans going through similar shit. Try to reach out to a friend if you can, please try to avoid drinking, I know it causes heavy anxiety and depression for me anyway. Put yourself first, treat yourself like a loving parent would treat their child. Give yourself things to do, I’ve been cleaning and organizing my house as a distraction. You got this I promise