I meant to add, Prozac withdrawal is an odd bird because it stays in the body longer than other drugs of the same class, so there's always been a question of when withdrawal starts with it.
You're pretty young to be on an ssri, and pretty young to be smoking pot. But if you're going to take an antidepressant, you can't miss doses, so you need to have a disciplined approach. And anyone who needs an antidepressant probably shouldn't be smoking weed, as it tends to reinforce what's inside of us. I'd try to use therapy to get to the bottom of this so you can get off the drugs, especially at such a young age.
I would say you need to tell someone. I have done this seveal times (including the weed part). The way it felt to me was that when I was taking my meds and doing good I was holding up this boulder and when I slipped I dropped it. You will likely need some assistance picking it back up but you can be there again.