Why would you want to dig yourself in deeper than you already are? Try being honest with yourself, and then be honest with everyone else, i realise it will hurt you to tell the truth, but in the long term who is going to hurt more....you or the child you now need to be responsible for, go to your boyfriend and tell him everything. Realise that he will be angry, hurt and may not want to have anything to do with you for a while, but face it, you are at fault and do deserve it, give him sometime, and allow him to face facts....he may be willing to step forward and be honourable about it, even though the child isnt his. And as far as his brother goes, he needs to take responsiblity too, he is also at fault, what was he thinking, taking advantage of his brothers girlfriend.
And as for no other men wanting you, stop living in the 50's, there are plenty of men out there that will take on a single woman and her child.