I Haven't Had My Period Yet Nor I Have Missed

I haven't had my period yet nor i have missed my period this month i'm usually late all the time i sometimes have to wait 3days of 1 week for my period anyway i feel something beating inside my stomach when i push my stomach deep back i feel this beating like my heart was beating inside my stomach i'm stressing alot i'm worryed i have never had sex or anything with a Boy ever in my whole life