I have an abcess on my buttocks which swells up doctor gave me penicillian 3 000 whick just made it bigger , opened it up it was filled with blood, pus?

Culture: Penicillin is probably the least likely antibiotic to be effective against staph aureus in this day and age. This needs to be fully drained and probably will require antibiotic therapy as well. Therefore, culture to isolate and identify and test for antibiotic sensitivity is necessary to decide what drugs can be used. See another doctor, perhaps a general surgeon.