Birth Control

So on Monday I went to my OBGYN for the first time and I was prescribed birth control. I made the appointment because I had my period nonstop for like 2 months and they've always been irregular (since I got mine when I was 11 and I'm now 17). Anyway so I had also told the nurse who weighed me/ took my blood pressure and asked questions that I've been recently sexually active. I know there are different kinds of birth control but is Lo Loestrin Fe a good one? And will it prevent pregnancy as well as regulating my cycle? Sorry for all the questions it's just a little awkward to talk to my mom about it. Also he gave me a sample of it, and told me to take it the first Sunday of my period. Should I go get my prescription or should I do my first pack with that sample?