My jeans always unravel in the groin, in the fabric just next to the seam. I was thinking it was because of bicycling, but it still happens (though at a lower r

My jeans always unravel in the groin, in the fabric just next to the seam. I was thinking it was because of bicycling, but it still happens (though at a lower rate) even though I no longer bicycle to work. Maybe I man-spread too much? :-) I would love some advice on how to deal with this, since I'm tired of shelling out $100+ for jeans several times a year.