Y did my ex contact me after so long?

The fact that you were his first everything, probably means your his security blanket a bit. But he left you and treated you bad when you were trying to be decent. He no doubt realises what he left and is trying to judge your reaction. I went through something very similar...5 times. That guy is now getting married after 9 months with someone else. I know it hurts and you want to believe, but the thing is, even if he does contact you...inside can you trust him again? He hasn't proven himself. Let it go. Let him know to let it go too. It is not fair to you. You need to finish healing and his constant bringing up of the past can do nothing but hurt you further and perhaps guilt you into a selfish relationship where he seems to be good at the taking. Be strong. Best of luck to you. He will move on eventually.