Without wanting to sound callous, it's all about damage control. If I had to sway one way, it would be towards abortion. If you don't want a child and you're damn sure your partner won't, I think an abortion is, ironically, the most ethical approach. That might sound absurd, but to me it sounds like your boyfriend wouldn't want to be involved and it hardly sounds like you are desperate to be a mother either. An abortion may be inhumane, but is bringing up an unwanted child without a proper quality of life/solid father figure any more virtuous? You've made it perfectly clear that you don't want a child right now, so why make such a massive commitment to something that not only is against your will, but against your own desire? It might be the height of altruism to raise a child that is unwanted, but wouldn't you be sacrificing your own life somewhat? You're 20! You should enjoy your life some more without such a humongous responsibilty. You have plenty of time to find the right man to father a child with you, when you are ready to make that commitment, because frankly, you aren't yet. Speak to your guy, see what he says. Don't let him decide for you, but you should certainly take into account what he says.
Like I say, it's a question of damage control. You're always going to feel ambivalence towards this. Do you raise an unwanted child that is likely to be emotionally malnourished? Or can you take the emotional toll of aborting an unborn baby?
My advice: Don't have a baby just because abortion is frowned upon. Do what you want to do, not what you think you should do or you are told you should do.