Hello and welcome to HCM.
Thank you for your query.
From your history, you do have an irregular menstrual cycle. It would not be completely unlikely for you to experience a delay. But, we will have to first and most importantly rule out a pregnancy
You could do this with the help of a urine pregnancy kit. It is best to get it done 20 days after last sexual contact and on first day of missed period. Although there are chances of a false negative report, kindly repeat this test with a 2 day interval at least 3 times to rule pregnancy out.
I hope I have succeeded in providing the information you were looking for. Please feel free to write back to me for any further clarifications. I would gladly help you.