Question about my bowl movements/anus?!

Your Immune system isn't very good? I would check with a doctor to have it checked out. It very well could still be the effects of the antibiotics, they take a toll on the bowels, but it also might be a digestive syndrome or disease.... IBS, colitis, ileitis, diverticulitis, Crohn's, or others. All are treatable and all but Crohn's are curable with surgery or less. The anal itching leads me to believe you may have hemorrhoids. I honestly am not some hypochondriac or anything, I personally and many members of my family deal with the ailments I listed and for several years so I think I could practically be a gastroenterologist haahaa... Just get it checked out soon so you don't have to hurt. Tell your doctor the exact symptoms and and he/she can decide if you need further diagnosis or treatment. Remember, it could be something as simple as a stomach virus that is strong against drugs, and the anal itching could be because the anus is raw from the diarrhea, so don't stress yourself out. If you want any more information feel free to e - mail me if you are comfortable with it.
( i know you don't know me from Adam.) I hope that you feel better soon :)

You have good and bad bacteria that live in your bowel. They live in a delicate balance. Antibiotics will sometimes upset that balance letting the bad bacteria take control. The diarrhea is your body trying to get rid of the bad bacteria. Try eating some yogurt, make sure it says "live active cultures" on it. If it keeps up, you may have to see the doctor again. There are antibiotics that will target that bad bacteria and let your body get back in balance.

It itches because you need to wipe...