I just wanted to pass along my congratulations as well.

I have BTDT as the unexpectedly pregnant college student and came back willingly with a planned pregnancy in my early 40s before it was too late. What does that tell you about the whole single parent trip? Oh, I've made my share of mistakes and live with my share of regrets and "could have should have would have"s, don't get me wrong, but I am just so excited about being able to encourage you in your own journey down that now-familiar path.
I'm not going to violate the UA, but I so hate hearing that "A" word myself that I am being very, very careful about who I tell about this new babe; if there isn't a genuine reason why they need to know (like my dance teacher or the guy on Craig's List who I bought Bean's bicycle trailer from) and they aren't going to be excited and happy for me, then why should I bring it up at all?
I also wanted to point out that the pregnancy hormones are making me (at age 42 with a planned pregnancy) feel very vulnerable and exposed and raw; when I was TTC, it was so exciting to think about carrying my OWN child instead of some man's, but now I find myself mournfully thinking of Bean as "The baby nobody wants except me."
Fine for a melodrama or a plotline in a soap opera, but it doesn't have much of anything to do with reality; I love my baby just as much as you love yours. However, I don't see any need at all to rush telling your ex about the pregnancy. HEAL from the breakup first! You don't want or need his opinions and you aren't asking for a handout for the procedure which shall not be named. Why does he need to know before you've even hit the 12 week milestone? You will be feeling much better physically by then and you might even be able to feel your little one moving not too much later than that.
A bit of time and space will do both of you good and if you decide that you want this man's name on the birth certificate and want him to be a part of your child's life, then it will be easier to switch gears to the "coparenting mode" from the "broken dreams of a relationship that didn't work out" mode if you've had a bit of a break from each other first.
I can tell you some stories about men's reactions....OH BOY....I've had kids with three different men, not counting this Bean who really doesn't have a father at all (although after fifteen cycles of AI, I feel like I've darned well earned the right to be called "Daddy" and get a card in June as well as being called "Mommy" and getting one in May) and not one of them did any serious bonding during the first trimester of pregnancy.
This is your time and your baby's time. You can worry about when and where and how and why and whether the guy fits in later.