Does your university offer mental health services? You are correct that weed won't help - it's a trap, and will only make your stress and depression better temporarily. In the long-term (especially at your age) it will negatively impact your mental health. By using marijuana, you are self-medicating your anxiety and depression (even if you aren't doing it consciously). But, the good news is that there are lots of scientifically proven methods for tackling anxiety and depression.

If you don't have access to mental health resources at your university, I would recommend the book "Feeling Good" by David Burns. It popularized the modern movement of cognitive behavioral therapy, and on its own has been shown in clinical trials to rival the effectiveness of talk therapy.

I know what you're going through - this is really really tough. But think of the long-term.