Need advice/opinion!!

So last night my boyfriend and I had unprotected sex. We are always very careful.. I am on birth control & we almost always use a condom. Last night we didn't, but he still pulled out. 
Today I've felt really nauseous & just off somehow. My stomach started cramping up earlier & I've had a slight headache almost all day.. am I being paranoid or could it be related to last night? 
I would really appreciate any help on this. I don't have any female role models to turn to for help, so I'm turning to you guys!!