Have cellulitis on my lower abdomen. had it drained by dr and put on bactrim (sulfamethoxazole and trimethoprim) for 7 days. could this be mrsa?

Yes, maybe MRSA: In otherwise healthy people, non-rectal/genital cellulitis and skin abscesses (that's probably what required drainage) are caused by strep or staph, and many staph infections are MRSA. So it's definitely possible. Bactrim (sulfamethoxazole and trimethoprim) is the recommended antibiotic because it covers them all, including MRSA. Most likely a culture test was done and will tell whether or not it's MRSA. Ask your doctor.