Guess I'll update too.
It's been a year now since my ex and I broke up over the kids issue...and I can confidently say that it was the best decision and I'm really glad I went with my gut and didn't have the kids.
We're still best friends, and honestly our relationship got a lot better once we stopped dating. It's been weird; I don't know if he realizes he's been doing it, but we've kind of been emotionally dating? At least, he does things that seem a little above and beyond the feeling level of best friend.
However, now that so much time has gone by, there are plenty of things he does that bug me, and at this point I feel like I could do much better for a partner. After spending some time with him and his daughter (7.5 y/o), I can say we would have had some conflicts in parenting too, something that never even crossed my mind. (ie Things he thinks are okay for the kid are not always what I think are okay. I'm not her mother, so it doesn't matter, but I can see there would be a lot of arguments if we had kids together.)
If I had any lingering doubt to whether or not it was the right decision, that was completely wiped out by going on a several day trip with the two of them this weekend. Actually, I highly suggest going on vacation with a young child if you are still agonizing over the decision, because it is an eye opener, not being able to get away from the kid for days. You get to experience fun things, like going to a water amusement park and not riding a single ride because the kid doesn't want to. Or having to watch her brush her teeth because if you don't she only brushes them for 15 seconds. Or taking 12 hours to make an 8 hour drive because you have to stop so often. Or repeating yourself over and over again, whether to answer the same question repeatedly (yes, we'll go do x, but not until later today) or to tell them to do something that they don't feel like doing.
It actually had such an impact, being full time partial parent for three days, that I'm also going to no longer consider dating anyone that has a kid, no matter how small their visitation is, because I hate being in that stepmother role, even for one weekend a year. Needless to say, very happy I didn't reconsider and have my own with him.
Summertime14, I'm sorry for the situation you're in. Like blackeyedsally said, only you can make that decision. One thing that worries me though is you saying you two were rocky the year leading up to the pregnancy...it seems from everything I've read, here and elsewhere, that adding a child in the mix is just going to exacerbate any problems you have. I would think long and hard on if you would be willing to be a single mother before you consider becoming pregnant again, because that is the worst case scenario and one you have to consider and be prepared for before making that leap, IMHO.
One other thing that might be helpful to the group: my ex was reading this book called All Joy No Fun, which looks at the effects that children have on the parents, versus the other way around like most parenting books. I'm only about a chapter in, but it's been good so far at talking about the real impacts of parenting, if you wanted to give it a look.