How to get birth control without parents knowing

I have a boyfriend and we partake in “activities” extremely often. We use condoms almost every time to avoid pregnancy. I am 15 (I’m sorry if it’s too young for some) and know that I DO NOT want a child. I’ve seen what’s having a baby has done to young teens like me and how it can ruin your life. Both my parents do not think I have had any intercourse and if they were to know they would freak out and even potentially make my boyfriend and I end our relationship which I do not want. I don’t know how to get birth control at an affordable price or even free. I know planned parenthood has options but I’m to shy to walk in and ask. What do I do and can anyone give me some tips so that I can get some?