Need advice !!!

My boyfriend hooked up with another girl today. He told me straight away, and he apologised over and over and cried to me (he never cries to me) I said to him "I'm not breaking up with you but you you talk to the girl or have anything to do with her or if she texts or calls even if you don't reply we are done" and he agreed.. I Don't know if I should give it one more shot or not.. We have been together 6 months this month I'm 15 he's 17, he doesn't party or anything and neither do I we have a pretty mature relationship. Helppp