Some advice

So I had sex 2 nights ago, my period is very weird and according to past periods I'm suppose to get it tomorrow. Since January I've been getting my period around ever 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.