I have shingles for the 3rd time. i'm only 28 years old. what is going on? should i be tested for other things?

Doubt VZV ?HSV2: You do not describe where your "shingles" are located. Varicella-zoster shingles only rarely recur especially in someone as young as you. If your lesions are anywhere near your genital area or buttocks it is probably herpes simplex virus 2 or genital herpes that is recurring. If this is the case valacyclovir tablets from your physician can prevent these recurrences.

Sure of diagnosis?: Are you sure that this has been a third bout of shingles. This sounds unusual. Insure that the condition is actually Shingles. If if has been Shingles each time - your immune system should be evaluated.