Reassurance

My boyfriend and I regularly have sex without a condom, however I am on birth control pills, and he pulls out before he finishes.

I take my birth control pills continuously, so that I don't get a period at all. This is not a personal choice, but a medical preventative prescription because severe endometriosis runs in my family, which can cause infertility in the future. Supposedly, taking my pills continuously can prevent endometriosis which will help me to conceive in the future if I choose to have children.

My question is: if I'm not getting a period at all, how can I tell if my birth control works, or if I could end up being pregnant? I'm 21, however I currently live with my parents who are strict and would not want me to be using pregnancy tests to confirm that I'm not pregnant.