This might be a bit weird but...
My crush and I have been crushing on each other for maybe 2 years? We didn't go out, we both just knew we liked each other.

We suddenly just drifted away and became friends. I was a bit disappointed but after that moment I had a lot of relationship problems with friends and guys. I was depressed... 82% was my score for depression.

Any advice?

Changes like this don't happen independent of each other. Of course we know nothing about either one of you, not even how old you are!
Crushes are usually a stage of youth, and they do go away on their own. If you were disappointed, why did you let it just happen? Did you wonder if maybe you haven't figured out yet how to speak your mind, say what you feel, ACT? That's common when young too. A lot of us sort of wait for other people to act, and assume that they know what to do, and let them run the show. There's usually a few who take charge and set the pace for how to dress and think and what to like, and others follow. Same thing with people you crush on. You wait for them to make a move, and they are waiting for you. It's possible that your depression is feeling that you missed out on a chance to be more proactive. Don't feel bad! It goes with the agony of being young. Learn from it, and practice BEING a person who has ideas and plans and wishes and views on life. Show that you have a mind, and choices, and make decisions. That includes telling someone you like them.

Its perfectly common to dwell to better times/people, when caught up in difficult situations that seem to linger. I think its best to resolve old issues that drag you down, and NOT obsess with what if's of the past.

If we do not act on our feelings, they change, Relationships are flowing, and changing all the time. So if nothing was done to be more than friends, friends is all there will be.