Every time I put in a tampon my period stops?

I got my period Wednesday and it typically lasts 3 days. My boyfriend and I were trying to conceive and were unsuccessful, yet the first day was extremely heavy and since day two every time I place a tampon in, my period stops. Once I take it out it resumes within an hour or two. I have never had this problem before, haven't switched brands or anything like that. Is this normal or a concern? TIA!