Can you Relate?

So I had sex 3 nights ago, my period is very weird and according to past periods I'm suppose to get it today. Also according to Glow. Since January I've been getting my period around every 15-18 days. So basically twice a month, and for about a week or more. Last one was Feb.28- March 10. 
​I usually see spotting a day before I get it, and I have not noticed anything at all. I'm also pretty sore near my lower right belly area. I know that might be because of the sex. I just want to know if any of you ladies have experienced what I'm going through.