period & sex

When I first lost my virginity I was so worried I was pregnant I stressed and it delayed my period but it came.
The next month I didn't even worry and it came 
Now this month I worried for it and it's late again 
How do I get it off my mind
I'm pretty irregular anyways 
Once it was 17th
The next month it came 20th
Then it came 19th
And now .. pending