Pregnant ?? Or just Nerves

Okay, I'm 16 and I lost my virginity to my boyfriend of 6 months 3 months ago, I had my period a week or so before we did it n I hadn't had my period since last week when it only lasted 3 days and so light it was barely there... 
But the last 2 weeks I've been so tired n feeling so sick it's not funny n it's not me, my stomach is bloated which I find worrying because I'm naturally thin with no fat whatsoever. 
Should I be worried about pregnancy at all ??