Pregnant? Yes or no...?

I would like some advice as to if I'm pregnant. I was on birth control for about 6 months, and got my last shot in January, and it would have started to become ineffective around March. I had a normal period from the time I got off the shot until May, when I had my last period. I get my period the last week of the month usually (it goes longer than 28 days usually). However, I've missed my period for June already, and I'm working towards being without my period for two months now. My best friend is pregnant, and she's usually my go-to for questions. I don't have tender , although eating chicken (which is my favorite) makes me sick to my stomach. I get tired easier, and sleep longer. However, in early June, I got a big promotion at work, and have received a lot more responsibilities. More than I've ever had before. I've probably taken 20 pregnancy tests, and I've gotten bout 5 positive out of all of them. I know that a pregnancy tests contains the HCG hormone and that is what a pregnancy test be positive, but what would you say about my condition? I have no excessive weight gain, no excessive weight loss, no emotional stress minus the work stress...please help!