Hello, This Is Shalyn Am 18. And I Live In

Hello,
This is shalyn am 18. And i live in Italy. A a bit worried about my periods there late, late of three months now. Me and my boyfriend we had sex. And just once we had sex without but he didn't cum inside. But this thing happened at the end of april later on we didn't have sexual stuff. By the way I did the pregnant test on the starting of june and the another one of the 05/07 but they were both negative. I can't go to the doctor alone cause my parents wont let me out like neve the don't even know I have a boyfriend and till school starts on September is should stay home.Please help. It never happened to me May just for a month but just once happened. Help me please.am worried.