I am 21, not married and pregnant...How do you deal when your ideal has been shattered?

I always was prochoice. If my birth control failed and I got pregnant before I was ready, then I would get an abortion. Well now that its happened it isn't so easy. I feel like in no way is it natural or should it be possible for a woman to choose to have her baby or not. I feel so naive and lost. I've only been with my boyfriend 5 months, less time than even carrying a baby. At first he was saying how his life is wrecked and he doenst want a baby. Its so frustrating because I dont want a baby right now either! And to top it off now he's not sure he loves me. He'll be there for the baby, but not me. I have always wanted to be a mother and I wanted to be happily married and have a career already. I still have another year of school and I am so scared to be alone with a baby. I feel like my whole life changed the instant I found out I was pregnant, something that I always imagined to be joyous, and now it seems tainted by this situation. My heart is broken..how do I do this alone?