I dated this guy in school a couple of years ago, and he was amazing.
Really sweet, caring and supportive.
We were together for a little under a year, during my early teens.
It was all perfect until one day he cheated on me with my classmate!
I was heartbroken, I had no idea what to do.
He showed me a side of him that I never even knew he had. He apologized every day for hurting me, but never actually admitted what he did, though I knew he did.
It was irritating, being lied to over and over.
He asked to get back together, but I never did.
I knew he was a bad person who would probably never learn.
Anyway, its been 3 years now, but I'm still not over him. I cry when I see him sometimes, I die when I hear about him and other girls. I haven't dated since then, but he has.
Is this even normal?

'Normal' means within the statistical norm, but of course it connotes something different.
So no, it's not the norm for a teen to be still suffering after 3 years.
It's also the norm for teens to play the field somewhat, because young minds and attitudes and feelings are changing so rapidly, and because there is so much to learn about life and people.
I suspect that there is something about you that takes hurt and lies really hard. It isn't so much feelings of love or missing him as it is wishing you knew what it was about you that he was willing to be so casual about - BUT we don't know how involved he was exclusively with you! When you are a 'young teen' (you don't say age), it's very easy to be unclear about commitment.

(PS: I think you might want to stay out of advice to married pregnant women in other countries. Your advice was 'off' to say the least, and reveals your age. Give advice to other teens all you want!)

You can't complain when you decided not to accept his apology.
Can't blame anyone but yourself.