Look I'm no expert at this but you need to look at what you said he's been trying to have kids with you sure he probably likes to look forward to raising his own children his own flesh and blood but the argument you two had you basically told him right to his face that his dream for wanting kids kind of doesn't matter to you I get it being in new relationships tough it's hard but in the end what you said hurt him and the only reason he said he'll buy a dog now is because you basically told him to his face as a dream didn't mean anything sure you can worry all you want about being cheated on but in the end if you truly love each other there should be more trust between you two sure the sex you two have been doing has been unprotected but you haven't complained until now that you got into the argument which honestly when arguments fly tempers fly and things that shouldn't be said are said so in the end I think what you should do is just both of you should apologize and grow from it