Can I be pregnant even though I started my period? I am extremely nauseous and my head aches.

Me and my boyfriend had sex a few days before my period. I started menstruating 2 days before I should have and since then I feel extremely nauseous, my head aches alot. This happens intermittently everyday.

I am a diabetic and my sugar levels have started going up since after all above happened.

Please advise at your soonest. I am really worried.