Im 15 years old , I haven’t gotten my period

Patient: Im 15 years old , I haven’t gotten my period in 6 months . During those 6 months I was not sexually active . Friday March 27 my boyfriend came over and we almost had sex , I was positioned on my back and he put the tip of his penis in me for a long time he almost went all the way In but I stopped him and he just had the tip in for a while , then I changed my position and we did doggy style . He went a little farther when we were in that position and he cummed in me a couple of times . Sunday March 29 I got my period and im very scared cause I haven’t gotten my period in a long time and I got it a couple days after me and my boyfriend were sexually active . Please help

Doctor: