Advice on first unplanned pregnancy

Here we go, I was casually dating this really great guy that I met after being in a toxic long term relationship. I just saw it as a casual rebound  But after a month or so he said he didn't see the relationship going anywhere, because he's very stressed out with school. I was okay with that because I wasn't looking for anything serious either. But a week later after he ended things I found out I'm pregnant. I'm 22 and graduate college in May. My estimated due date is in August and by then I'll be 23. I live on my own and have a very dependable job. The father is in his first year of medical school and he's 28. He's such a mature guy and so kind. I told him I wasn't keeping it, I didn't even think about it, abortion was just a reaction. I couldn't believe I was pregnant. He's supports the abortion and says he will pay for it. But with each passing day I keep thinking of my baby and I get emotional. I think of the future and how much I would love my baby. I'm just so lost. I want a baby, but I want to be married or a least dating someone I love. I don't know if I can raise it alone. This has got to be one of the hardest decisions in life. Anyways, I just want to know how did you know you were making the right decision?