Hmmmm....You have quite a lot to think about. You say that you hope you are pregnant....In which case, are you set up to do this on your own?
If the potential father is going to put pressure on you to abort, then I wouldn't tell him! You are going to have a lot to deal with and having some fella, giving you extra emotional stress is not what you need. Sit down and have a good think about what you intend to do. This is your choice and your body.
However, if you intend on having the baby and then going after the father for child support (of some kind) then I would say that he needs to be told. I think that you need to really think long and hard about what you intend to do and then make your decision.
Good luck. I hope things work out well for you.
Xx