I have been there, oddly enough it was after I already had two beautiful daughters. I went out and was careless when my marriage broke up. The worst possible timing. It was going to be hard enough to take care of my daughters on my own, now I had a new life to consider. I could not bring a baby into such a bad situation, and I could not ask my children to share what little we were going to have with another baby. So I had an abortion.
Now the reason I am telling you this is because at that moment it seemed like the only option, and not long after I suddenly thought "that was not a good enough reason". So I understand exactly what you are going through. Its like a remorse thing. But you have remember how you felt at that time, your reasoning at that time. the turn of events with or without the abortion. And the future for your and your future children with or without the abortion. I bet you will find you made the decision for all of the right reasons.