@MissApril,
Wow, there's a lot going on there.
First off, the fact that he's consciously committed to you is a good thing. It tells me that despite anything else he's feeling, he's chosen his voluntary commitment to include you. So, that should bode in your favor.
Ex's come as baggage - baggage that can't be disclaimed or sent ahead. You must carry it with your mate or get rid of them both; there's really no disconnecting it. Also, you can't fight an ex because you'd be battling with a set of memories to which you're not privy: Only the person who had that bond can put their past experiences in context with their current relationship. If they - by cause or lack of action - allow memories to infringe on their current relationship, it'll be up to them to recognize and fix it; and its not going to fix itself.
So knowing this, I'd advise you to express your concerns and set down any "lines in the sand" that are important to you (borders, "don't cross this", etc.) then simply trust - or ditch the relationship and be done. Whether or not you're OK with where he places you (and the ex) in his attentions in the pecking order can't be known until a good deal of time has past.
There are some causes for yellow flags here, that make me want to toss you a big "Caution" flag:
- Twice now he's impregnated women who, twice, had to give him the boot.
- That he had no desire to reconcile with you after you first left (that indifference)
- That he can't seem to connect with you now
... all should tell you: Proceed with Caution
If he's actualy chasing her then your decision is simple but difficult: Stay and take what you know has likely not been resolved -or- Leave and lose what you do have. Staying gives you the chance for a big payoff down the road, but at what cost? Leaving puts the pain on you now but could free you from a situation that might not change.
Bottom Line: No clear way, take stock of your priorities and tolerance levels and give a sharp ear to what your gut's telling you.
Good luck