It happened to me at 23 or 24. She's now my wife, but this was like a month into our relationship and neither of us were ready to be parents together. We ended up getting an abortion which cost me every dollar I had at the time. I believe it was the best decision we could've made at the time, but it really fucked my wife up for a long time. The times she broke down about it were completely random, and happened pretty much until our daughter was born, and that was like 7 years into our relationship when we were ready for a baby.
Because this is already your ex, I'd seriously consider talking about this with her and how the two of you will now be connected for life if she chooses to keep it. Do you both want that, or is it the best decision to go through with the abortion and give yourselves the chance to move on? Just know that it might be a much more emotional decision for her that it is for you, so be there for her.
Parenthood is the best thing that I've done with my life, but it was a conscious decision my wife and I made when we were ready for it. I can't say it would be different with an unplanned child, but the whole thing should be something you're excited for, not something that makes you anxious. I wish you the best, man.