My roomate is wearing my tshirt

A noticed it a few days ago and I thought that it could be his own. But he hasn't changed for 5 days now and he keeps telling not to me but to his other friends who come to room,I don't got no extra t-shirt he says all are soiled.

Now I am 80% sure it's mine what do I say.

I think he has seen me looking at the tshirt with a confusing look and I didn't even ask him as I mean why would anyone do this.