Arm implant vs pill

Hey ladies!!

SO I am 16 and I have a boyfriend and we’ve been together for about two years and we want to have sex eventually. I don’t just want to use a condom because I don’t want to get pregnant obviously, but I also have issues with my period and I want to be on some kind of birth control for both reasons. I get cramps about two weeks before my period and a week after and I bleed before my period. I’m worried that with the pill, ill gain weight or be extremely moody and everything but I also don’t know if my OBGYN will ask me if I want the arm implant since i would be going for my period since I don’t want to tell my mom I want to have sex 😬 can you guys give me advice? Would my OBGYN ask me if I want the arm implant? Thank you all