I get a rash on my stomach twice a year over a healed chicken pox bump and it last for 1 to 2 months and itches like crazy . what can it be?

Needs to be seen: Skin rashes are notoriously difficult to diagnose without being seen. You should see your primary care doc or a dermatologist, preferably when you are having the rash. That is the best way to figure out what this might be.

Shingles?: Shingles is an often recurrent vesicular "rash" that typically occurs asymmetrically, and may be associated with discomfort. Don't scratch it! to be certain of the diagnosis however, so appropriate treatment can be offered, the eruption should be evaluated medically when active.