Regretting abortion

I just want some advice on this no hate please... basically I had an abortion in October, I had been with the father for 9 years we have an 18 month old together but we had split up not long before I found out I was pregnant. He accused me of cheating, was very verbally abusive towards me and I was severely depressed so i chose to have an abortion to work on my own mental health and be the best mom I can be for my little boy. At the time I didn't regret it, but now 6 months down the line I cant stop thinking of what I did. I took a sibling from my little boy, one who would of shared the same father with him. I have friends who are due the same time I was supposed to be and it kills me that I'm not having a baby (even though it was my choice). I just know if I was to get pregnant now I wouldn't have an abortion but feel so guilty for the one I did have. Has anyone else gone through this? I have positives in my life like I'm starting uni in September which I wouldn't of been if I kept the baby and I have an amazing job but the guilt and resentment on myself is always there and I have no idea how to deal with it 😭