Advice needed!!!

Lately I feel like my boyfriend is hiding something. Like he lies all the time about stupid little things but then a few weeks ago he took a girl to lunch but said she was just a close friend. He has also been messaging another girl and lying about it. And to top everything off the sex sucks (TMI for some, I apologize). But once he finishes he doesn’t even care about me anymore and he doesn’t put in any effort with it anyway. But on the other hand when he wants to be sweet he can be really sweet but he just seems to be in a bad mood more times than not lately. I just don’t know what to do.