Sex with condom and birth control yet feeling uneasy

My boyfriend and I had sex 13 days ago. It was protected with a condom (it did NOT break) and I have been on birth control and taken the pills as directed. Since then, I have traveled back home for the holidays and I found out my friend got pregnant as well as my cousin (both unplanned). Since then, I have felt sick and so uneasy. I worry about it constantly and even bought a home preg. test. I took both that came in the package and both came up negative. I was satisfied until I found out that I probably took the tests too early.

Since then I feel uneasy and my stomach unsettled. I've been tracking my weight and I've actually lost a couple pounds. I am not hungry at all. I am sleeping regularly (no more or less than I usually do). According to the normalcy of my birth control pills I should be on my period in about a 1.5 weeks.

Should I completely discount the negative tests I had already?
Am I mind screwing myself into thinking I am pregnant?
My boyfriend and I have been so careful so I am trying to be logical and go with statistics here but I still feel so uneasy and worried.

Please help.