I've been stressing out a lot about this. I don't know if it's paranoia or stupidity.  8-|

I had sex, but then got my period later for 5 days which is pretty common. I don't remember if it was light or heavy - I can't tell if maybe it was implantation bleeding. I only started stressing out when I found out my period afterwards was 3 days late. I am now 6 days late, with a lot of cramping and bloating, white discharge and loss of appetite. Last night, I kept feeling bile in my throat.

It's very rare for me to have a late period. I have never missed one!
I haven't had a change in diet or exercise, neither have I have been stressed so I have no idea what could be causing me to miss my period. It has been about 5-6 weeks that I have had sex.

Please help! I don't know what to do. Should I just get a HPT or see my GP?
Am I just paranoid and stressing over nothing?
If I got my period after sex, doesn't that mean I'm not pregnant 100%?

I appreciate any advice and help!
Thanks :-)