I took it all for granted...

Hey girls. I really debated posting this but I just have come to the point where I want some advice that isn't from friends or family... 2 years ago I broke up with my boyfriend of one year. I was getting ready to go to college 8 hrs away and he was staying, hoping that I would stay too. Things fell apart and we started fighting more and more... long story short, we just both agreed to end it. He was my first love and I believe I was his, which has made me getting over it that much harder. For the next years to come we tried to make it work, we always found our way back to each other.. he told me he couldn't bear the thought of life without me and that I was the one for him... I believe we are meant to be but last year my stupid self couldn't swallow my pride and take the leap of faith to try again and he moved on. He's dating another girl, and I thought I had moved on too until about a week ago when I woke up with this overwhelming sense of sadness and longing for him. I've been thinking about him nonstop and I just keep feeling like I need to tell him how in love with him I still am and tell him that I think he's the one for me... but I know he is in a relationship. What do I do?