I stole this idea from a film and I LOVE it...
The minimins team will ring his doorbell, when he answers one of us will punch him in his man business, and when he's on the floor crying and asking why we will all say "you know why!!!"
... So tell him anymore dis-respect and/or funny business and he will need to find a butler to answer his door for him!!!
On a serious note, big hug to you! Some relationships in their infancy have ups and down doesn't mean the relationship is ruined, but might mean that ground rules need to be discussed and you can lay down your bottom line i.e. sex or implication of sex with other people = completely unacceptable, then see ball punching example above etc.
However be aware that this may have had a massive impact on your trust and as much as you care for someone if the trust has been damaged it's so hard to get it back. I drove myself mad with my ex, checking his phone, email, riffling through pockets... now I eventually caught him cheating... or did I drive him to it... I'll never know for certain, but being in a relationship without a certain level of trust was absolutely exhausting, not fun and made us both more unhappy that happy... Not good!!!
Good luck, listen to both your head and heart and find a compromise... as long as you are not for one minute compromising yourself!!! x