Freaking out a little...

So ok I typically take my pill at 9pm, sometimes I forget and take it the next morning/ next day, but my SO and I have sex very frequently. Tonight him and I were hanging out and all of the sudden at like 3:00am I got really nauseous, I have no other symptoms of sickness, it's there a way to tell if this could be a symptom of pregnancy, how likely is it that I could be pregnant...? Edit: This is also only my second pack being back on birth control.