Yeah, grinding is a form of cheating. It might not be as bad as sleeping with someone else, but the intent is still the same. Why is he grinding up on random ladies when he has a girlfriend? That’s just low class. Plus, unless he’s paying to have a stripper grind on his lap for night school money, it rarely ends with just grinding. If he’s rubbing up against a random woman at the club the implication is a) he’s single and b) he wants to–pardon my slang–”bump uglies” with her.
Did he cheat on another girlfriend with you? That doesn’t mean he’ll definitely cheat on you, but it does mean he’s capable of it. That said, unless you have proof that he’s cheating — relax. Let him go out with his friends and blow off steam.
Don’t just assume he’s trying to cheat on you. It all comes down to whether or not he acts trustworthy. Does he come home at 3am reeking of booze and cheap perfume? Is he flirty around other women? Does he never want you to come when he goes out to the club? Yeah, his friends might have his back, but chances are they’re good guys who don’t want him to cheat and get into another bad situation. Plus, it isn’t really their responsibility to keep him in line. If he’s going to cheat, that’s all on him.
So if you’ve seen or heard about him grinding on randoms in the club, that’s definitely grounds for dumping. But if you’re just assuming that he’s hitting on other women when he goes out with friends, try not to worry. Talk to him and let him know that you’re worried he’ll cheat since it’s happened before. Hopefully he’ll do everything he can to show you that he’s faithful.