Some time ago, when I was still with my last girlfriend, we had a rather heavy petting session in which the thong she was wearing ended up very damp. I commented that it must smell of her pussy at which point she whipped it off and stuffed it under my nose. The musky odour was indeed heavenly, and probably started my panty-sniffing habit. She then dared me to try the thong on. I refused saying it wouldn't fit me, but she insisted. I managed to pull it up over my hips, and the thin back rose up between my butt cheeks. The front of the thong was a thin see-through material and my girlfriend commented how it cradled my 'package' very nicely. She began stroking my cock through the thin material and I was soon rising to the occasion. I lay down on the bed and she pulled the thong up to cover my whole cock, and began rubbing up and down with the flat of her hand. The friction was very stimulating as she moved from between my balls up to the head of my cock. I closed my eyes and reveled in the experience, feeling that tingling between my legs knowing I would cum soon. Not too much later I felt myself cumming and the jism squeezed itself through the thin mesh and pooled around my cock and stomach. Having my cock and balls encased in material whilst orgasming was a different and not unpleasant feeling.
Since we split up, I found a couple of pairs of her thongs among some clothes she had left behind. I occasionally slip one on for a wanking session and remember the great feeling when cumming through that thin material.