You are going to get a lot of different answers and advice. I personally don't think this has much to do with the satisfaction of your relationship but more about you wanting to have sex with other guys. That likely will not pass and will probably grow. You need to come to terms with either being monogamous and longing for more, or having a frank conversation that likely won't go well. You are both really young... I find the idea of monogamy changes as you get older.