What Causes A Red Abcess On Lower Left Side Of Abdomen With History Of Having Gastric Bypass?

I currently have a pretty bad abcess located on the lower left side of my abdomin, right above my pelvic area in addition to some smaller patches of sores in different areas including where my pubic hair is along with my face and a few in my nose. I did have a miserable bout with MRSA in May and I am experiencing similar symptoms. Unfortunately I relapsed on alcohol and methamphetamines in May mainly because I was so tired and week. I already lack iron due to Chron s disease and having had the Gastric Bypass I don t absorb nutrients and vitamins the way I need to to function. I stopped using mehtamphetamines however 3 weeks ago after my Doctor randomly drug tested me before refilling my pain medication and I finally just opened up to him and became transparent about my current struggles. I saw him again last Friday however the abcess was a small red bump at that time so I hadn t talked with him about it. He swabbed my mouth because I could not give him a urine sample and just received those test results back which it states I am positive for mehtamphetamines even though I have used them in 3 weeks. I was on Humira until I had MRSA and was taken off but now I am down to 135lbs I am 5 9 , I have lost 20lbs in 5 weeks and I don t think my body can fight off another infection yet I am too afraid to let my Doctor know because of my drug test. Any advice?