Husband won't believe me

So my husband has this strange obsession with needing know if I masterbate , I honestly don't do it I don't want to and he refuses to believe me he even checks my underwear to see if I did and says I use clothes to lay under me to catch my fluids while I am he says because I have a lot of discharge on my underwear that I masterbsted and I haven't idk what else to do it's ruining our marriage I love him so much. I just want him to believe me I wasn't faithful in the past but but I am now and I'm trying to prove to him I only want him how do I get him to believe me when I say I am not masterbating

Husband won't believe me