Could I be pregnant?

I had sex 4 weeks ago on this up coming saturday. I got a period for this month. the first 2 and a half days the blood was orangey red medium/light flow..then it turned into brown spotting.I had sex yesturday and bright red blood came just when i wiped.Today i had no blood.its been 6 days since my last period started.
Before I got the period I was having dizznyess and light headedness and head aches if i dont eat, i was sleeping so much, I always felt exhausted, nasea that comes and goes and constant belching.. All of those symptoms are lightening up a little except for the constant belching, and if i even rest my arm on my stomach is feels like theres so much pressure on my stomach that somebodys pressing straight into it. I still have some nasea .I took a really cheap home pregnancy test tis morning and it came out negative. ANy ideas as to whats wrong ?