What are these holes in my clothes?always in the front by the waist?

first i thought it was from belts as it always seeems to happen to t-shirts, small holes the size of a swan vesta head grouped together maybe 2 or 6.But then someone suggested moths but no other clothes such as dresses etc are affected.It really is only my t-shirts come to think of it.What is it? the belt i mostly wear is the smooth metal fronted kind that threads back onto the materal belt strap anyway.What is going on here detectives anyone?