please read my story and tell me what you would do..

I'm 19 years old. I first got pregnant at 16 and had my son at 17. Then I got pregnant again at 18 and had my daughter at 19. She is five months old and I just found out I'm pregnant again. This last pregnancy was very unexpected and I tried being careful. I was planning on starting this program in the fall it would be full time school for a year to get my high school diploma and college credits at the same time it would be really good for me and my kids only issue is I can't do it if I'm pregnant again and I really don't wanna bring a third child with no high school diploma I already made that mistake twice. I never agreed with abortion till being in this situation and I'm highly considering it. I could really use some advice because which ever choice I make will be very life changing please tell me what you would do.