Again this alerts me. The first thing that I thought while reading this is: he’s cheating on you. I have a feeling he’s trying to hide something from you. It could be that he cheated on you with a whore and possibly has an STD’s or something and THAT’S why he’s being secretive. That could also be a reason for him not wanting to be intimate. Also he could be locking it because he wants to masturbate? How do you know for sure that he was dropping his excessive wastes? I mean do you go in there afterwards to inspect the bathroom to make sure the droppings have landed? “aha, yes I smell it. I see it. You may now be excused…”
p.s. hide a camera in de bathroom. That way you can find out
why he locks it and
what he's doing in there. And don't forget to come back here so we can help you analyze his behavior in the bathroom.