A:Oh, brother. I agree with tyrebite, you screwed up BIG TIME! How ever did you manage to end up in such a predicament?
OronD is right as well, you certainly do not act as though you loved your boyfriend or else you would not have left him and then been intimate with another man.
You most definitely have only the two choices - abortion (telling or not telling, as you deem proper) or total truth to both men and take whatever consequences arise. If you cannot decide what would be best to do, I suggest you get immediate counseling so you will have time to determine your preference before it is too late to take action.
It is only too bad that the biggest victims in this mess are your boyfriend and your unborn child.