Concerned

Last month I missed my period or at least I think I did. The one day I did see what I thought was my period it only lasted for a short time maybe a couple of days. It was just barely there. I have yet to take a pregnancy test in worry of getting a BFN again but am wondering could it have been implantation bleeding. My breast are now tender and I've felt a little bit of cramps since then but still no period. Not sure if anyone else has had this problem or could share some insight on what to do.