Talking to Parents

So I’m 15 and have really bad period cramps. I also have been sexually active for a little over a year. I mentioned getting birth control but my parents got extremely angry and thought I was just using it as an excuse to go have sex. Obviously I already have sex and that isn’t why I wanted the pill, but I can’t tell them that or we’d have more problems. Idk what to do. Any time I mention something like this they get mad, and one time my mom told me that if she found out I had already had sex she would shoot herself.. anyone know how to help? 😬