How Can Irregular And Delayed Periods Be Treated?

hi.im 34 years old. single.i had irregular periods..my cycle is from 30-40 days..smtimes exceed to 42 days also..n the flow is from 2-3 days. I had sexual intercourse once a day in a month that too using precautions.i had my ultrasound done,everything is normal.Do sexual intercourse is this the reason which is causing delation in the periods?I also take stress?plz help me out in having regular periods.last month i had sexual relationship...now its being 7 days over i didnt have periods..can u advice me???