Being a changed guy still in love with his ex, I don't think it's a TERRIBLE thing to look back and maybe give things another go. That's if they really changed and you still have that chemistry.
You have to be logical though. He is talking about getting married and kids and you guys haven't even been dating for a while. That's getting way ahead of yourself, like he knows you still care about him and you could just jump to that level at any second. That's absolutely wrong and would never work out with such illusions of grandeur. It'd be one thing if he left you alone to let your relationship pan out, but the fact that he wants to interrupt shows he has no respect for it and you. He let you go and shouldn't get to have you when he wants....
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.