pregnancy test came out positive

I have 2 kids already. Me and my fiance had sex two days before Halloween but I'm taking these diet pills. I thought I couldn't keep anything down because I thought the diet pills were making me sick. so I start to have no energy and got sleepy more than usual. Again, I thought it was the pills or the virus that has been going around because of the sometimes diahrea and stomach pains. I can't keep anything down so some told me to take a ept test just to be sure and it was positive...I had my period on the 3rd of this month. I hope that test is wrong.