Could I be pregnant or am I just freaking out?

You are definitely freaking out way too much. However, it's justified and a scary thing. You are not pregnant - just overly stressed out. You seem to be doing the right thing - getting on birth control. It may take a bit of adjusting, but the good thing is that the pill gives you lighter periods than before you took it. So don't let that fact throw you off or freak you out either. Stay strong with the BC and relax. You're not pregnant.