My girlfriend could be pregnant? please help?

Ok i been a nervous wreck all night tonight, i can't sleep...so i been up just listening to music. Ok around 9:00 last night, i was just shooting hoops at the court, my girlfriend came by and told be she thinks she is pregnant because she missed her period. So i said i would go with her to get a pregnancy test at the drug store but it just closed when we got there, so we just came back to my place and just hanged out in my room. She is so scared and i just held her in my arms until she felled alsleep. What if she is pregnant, what should we do. We are only juniors in high school. I will be there for her if she is pregnant, i won't leave her side but this is totally unexpected if she is pregnant. We talked last night and she is afraid to lose her perfect body. How do we tell our parents...idk i am so confused, what do we do. please help someone, we are both too young to be parents. I wont be like one of those boyfriends who run, i will stick by my girlfriends side but what do i do. HELP