Starting Birth Control ! What to expect?

I’m about to go to my OBGYN for an appointment soon in 2 weeks for my Birth Control. I’m 16, bout to be 17 in December 11. I am sexually active and I am always paranoid every month thinking I’m pregnant because my period wanna play games with my mind. I told my mom that i need it because my period is irregular and my cramps are horrible WHICH is true, I’m not lying, just leaving the other reason why I want BC LOL

So i wanna know how the process will be like when i go to my appointment? Will they run test on you, if so, like what? or do an ultrasound? What should i expect?

What’s your experience like?

Thanks 😇