Here is a great life hack that can help you make sense of the world. This one weird trick can be your guide when you're trying to sort out what's true and what's false about the teeming masses of humanity.
Whenever someone makes blanket statements about the human condition, that person is almost always talking about himself.
If someone says “men have needs and if those needs aren't met he will cheat,” he is not talking about men in general, he is talking about himself. He is saying “I have needs, and if you do not meet those needs, I will cheat.”
When someone says “if people don't believe in God, they have no reason to be good, and without God people will run around committing crimes,” what he is saying is “if I don't believe in God, I have no reason to be good, and without God I will run around committing crimes.”
When someone says “people can't be in love with more than one person at a time,” they're saying “I can't be in love with more than one person at a time.” When someone says “you can't have a threesome without being jealous,” they're really saying “I can't have a threesome without being jealous.”
Your boyfriend has just told you to your face that if you don't give him sex when and how he wants, he will cheat on you. He's trying to convince you this is true of all men; it's not.
You can't even say “all men have two legs,” so saying “all men will cheat if you don't give them whatever sex they want” is clearly absurd.