birth control

GF
I'm 15 and I have sex maybe once or twice a month with my long term boyfriend. I hinted at my mom that I wanted to be on birth control the other day, but I never said full out that I was meaning birth control and I really don't think she got the idea of what I was meaning. I was telling her that my periods are really heavy and that I have them twice a month (which this is all true). I don't really care to have it for my period, because I can deal with that, but I want it so my chances of pregnancy will be smaller. we always use a condom, but I still worry 24/7 after we have sex. I cannot think of another way to tell her I want to be on it without just straight up telling her I have sex. any advice or suggestions would be helpful! TIA