how can i get birth control?

so i’m 17 and ive been dating my boyfriend for a few months now and we’ve been very sexually active. we always use condoms except for today during the first two minutes of sex we tried it without a condom and it felt so much better. however, i have a really strict dad and i don’t think it’s possible to get the help i need and ask for it because he can’t know im sexually active at all. i turn 18 in three months but won’t he still find out since i’m under his insurance plan? how can i get birth control, if possible, at this age?