Pregnant or not

I had sex over 3 weeks ago and was meant to start my period yesterday , I’m normally 2 days early with every period But have not started it. A couple of days after having sex I started to have a uncomfortable feeling in my belly and feeling a bit sick when I woke up in the morning and the uncomfortable feeling last through the day , I was aware of people having symptoms over the 2 weeks wait but I have done a test and all come back negative , I haven’t being eating as much as I feel really full and bloated after a couple of bites and going to toilet is a big no , I’ve being to doctors and they said it was nothing to worry about and just got acid reflux , I’m just a bit scared now because my period hasn’t come yet the test come back negative