Pregnant with a 1 year old.. don’t know what to do.

Before anyone says anything i was on birth control. My period was 5 days late so today i took a pregnancy test which turned out to be positive. I took 4 total and they’re all positive... i have a son who just turned 1 this month. His father and i have had a rough relationship, he always leaves me and comes back and he isn’t reliable and i don’t trust him. Now that i know I’m pregnant I’m freaking out, I’m only 20 and I have 4 months left in college before i graduate. I’m far from ready to have another baby, but i know i couldn’t live with myself if i aborted or gave it up for adoption. I did not expect to get pregnant at all and i feel extremely depressed. My son is my world and i can’t imagine having to spend time with another baby and give him less time. I’m at a loss. 😢 the dad doesn’t want me to keep it and says we aren’t ready and i know it’s my choice but he is right. I just don’t want to get an abortion and hate myself after..