I agree with latoboy, It seems the nepali guys is really serious about the relation. In this context, what I suppest to you maples if he got to know the truth about you and the relation between you. I know its not so easy to tell things, but you have to take certain step. Just see which one will be less worse. If you love someone, keep loving him i.e. urs american bf. You have sympathy for nepali guy not love (as u have said u don't love him but..). Just manage to inform the nepali guy about the truth and continue with your existing relation. But realize that you have hurt some one badly and you deserve to hear whatever he says to you. Just be cool and accept that you have not been faithful to him. You cannot make good at every corner. All the best.