Husband constantly lying about porn

I’ve caught my husband on multiple occasions jerking off to porn or looking up porn. Which I get is t that big of a deal. But what hurts me is I’m constantly asking for sex and he’s always telling me that he’s not in the mood. Yet he’s in the mood to go watch porn...worst part is he tries to hide it from me and even lies to me about the last time he’s done it. Well tonight I found out he’s been lying again. I told him the next time I caught him lying I was gonna leave him. But tricky part is I’m 5 month pregnant. I get it sex during pregnancy is weird for some guys once u reach a certain size with the belly lol. But am I over reacting? Should I stick to me word and leave? I’m afraid if I co to ur to stay it’s just a never ending cycle and I’m constantly gonna be hurt and not trust him.