Pregnant??

I am currently 12 days late on my period. The story is kind of different. Around April 7-8 me and my boyfriend had sex. We have only done it once, just because our religion, we actually shouldn't have even done it at all.. but it happened. Exactly 1 week later I got my period. But I didn't have one at all during may. I'm very regular with my periods. I took a cheap test and the second line barely showed up, but I can see it. I took an expensive one the next day and it said negative. I don't have an appointment until next Thursday, I just wanted some opinions. Pregnant or no?