What should I do?

Okay, so I'm 18 & so is my boyfriend, and we've had sex multiple times, all except once, with a condom. The first and only time we didn't use a condom, he didn't orgasm or anything, and every time we used a condom, it didn't break nor were there any holes in it to my knowledge. What's weird though, is that I haven't had my period since the end of April. We had sex in mid-May, and once my period was late, we both really started to worry. I've taken 3 at-home pregnancy tests, all of which were negative, and all after my missed period. I'm just not sure what to do because I don't know if I should call my doctor to have a blood test done but that might require me telling my mom, and I know she'd lose it if she knew I had sex even though I am a legal adult. What should I do now?