To begin with you have to be sure who the father is. And then you must sit down and talk to him. Find out whether there is a future for you all or not.
If not, it might be time to have a chat with the other guy and see how he feels about a relationship with you and a baby on the way.
If you decide to go it alone then you have some serious decisions to make. Abortion is a very personal choice and you are the only one who should make that decision. Do not allow anyone to push you to make this decision as you may have some regrets down the road.
You need to decide if you want a future with either guy and then find out if the one you choose is okay with the fact that you are pregnant. If it turns out that neither of them is interested in a relationship. Then it will be time for you to talk to a professional before making the decision to have an abortion. No one must be allowed to make this decision for you.