long distance relationship 😭

So, my bf and I have been together for almost 6 months and I'm crazy about him and he's crazy about me obviously, and in 2 weeks I'm moving back to my home country(Brazil) I've been here in America for 5 years. He said he wants to do a long distance relationship and I told him I'll come back in 4 years because I'm just going there for college. But I also want to tell my mom that we've had sex and tell her everything, like keep her updated about my sex life because I want her to know about it. I just need help on what to do. What should I do? Oh, and I'm 18, and my bf is 20!