For any abcess in the groin or rectal area you should seek medical attention. You don't say how large it is, only that it has enlarged by 100% since you took antibiotics. If the abcess larger than 1/2" across you need to have it lanced and drained. The inside of the abcess contains pus and bacteria, you want to be sure to get it cleaned out thoroughly. Do you have a red line leading from the abscess? If so, you need to get to have it treated QUICKLY. Since it's the weekend, your only recourse at this point is to go to the Emergency Room. DO NOT ATTEMPT TO DRAIN IT YOURSELF BY SQUEEZING OR PRESSING ON IT. It's in a bad spot being in the groin and you can force the bacteria and poisons from the pus into the deeper tissues. You have lymph nodes in your groin, you don't want to force the material into that area. That's why it needs to be cleaned out by a doctor.
Ghilly
the abcess has enlarged by 100% since i took anti biotics and looks like it is going to burst and release puss