cheating!?/being secretive!

My boyfriend, has started to get himself off, behind my back. I only know because, (it sounds disgusting) he has a blanket where he wipes his cum and washes it after, and because obvs sometimes there is dried cum on his belly. It is over porn, as one time i called him out for it and he told me. I cant help but feel im not good enough and i cannot please him enough. Especially as its been hard for us to have sex as im nearly always batteling a uti/thrush. I feel like crap, and he dont even tell me when he has, or asks if i can please him. I have to find out for myslef otherwise he wouldnt tell me. Should i be so bothered he does this ???? What does everyone think? And why is he bieng so secretive ??‭‭