So much love to you; this sounds incredibly hard. I went through a pregnancy & abortion when I was about your age and in grad school, and the experience was hard but okay — mostly because I had an amazing doctor and a really supportive network. (I had a surgical abortion, rather than the medicine-induced one.)

My only advice would be to avoid thinking too much about "responsibility for your actions" — it sounds like you were on birth control. Even if you made a mistake, try to separate the "responsibility" from the choice you're making now. Forgive yourself, and make this choice with as much kindness and grace to yourself as you possibly can.

Listen to yourself, talk with your boyfriend if you feel like he can listen, and (depending on your school) consider seeing a school-health-center counselor or other professional who can help you work through what you're feeling.

When I was in your position, it really helped to think through what it would mean for my life, what my relationships and options would look like given each option, and what kind of relationship/home I would be bringing a child into.

Good luck, and try to be gentle with yourself.