Cycle changing

Ayla

Hey. So I'm 15. I've had my period since I was 10. Ever since I was 11 my periods have been a regular 28-29 days. I think my hormones are a little different now. I've been getting my period around day 35. Today I'm on day 31, and it's really weird for me. I'm not pregnant. I've had my period and it's been normal. We didn't use a condom, the two times we did it. He was clean too. I think this is a normal thing. Thoughts?