Its ever so common for the cheater to accuse the other partner. Now you discover stained underwear. It's a very very good chance he is or did cheat. I speak with authority as I WAS a serial cheater. It all depends how you feel about him cheating or having an affair.
Some spouses can be pretty forgiving. Others like my ex put me on her probation list that never ended for years and did everything she possibly could to make me pay for my crime.
Hope you fare well with the Hurrican
Relax, he got some pussy on the side. be more concerned about him leaving your ass. a lot of men love their wives and would not leave them but get that side pussy all the time and sometimes that side ass or cock. or maybe its all in your head. try to find out if its only sex or if he wants out. if its only sex, he loves you but releases stress by fucking some random slut he will never be with. take a chill pill and see what's going on first before you act crazy. men have a lot to deal with and you are told half the of it because women cant handle it sometimes.