Periods about to start ? Implantation ? or pregnancy ?

We are TTC from last 4 months, In the last two months my wife had a pain in her legs on and off during the whole day, then she staarted to use multi vitamins ( including Folic acid ) and the pain vanished, later last month she again had this twinges like pain in he leges mostly left leg just a week before periods, and this time its around 4 days to her period and she is again having the same pain but on both legs this time... She is also feeling tired and has a bit tender .....Is this again a sign of period ? or it could be implantation or pregnancy sign ? I know we can test it but she is afraid to test before the starting date of next periods ... She never had this pain before her periods when she was unmarried, ......... Another thing I wanna ask, ... I have read that sometimes very early miscarriage can also cause pain, and one cannot even differntiate between that miscarriage and period ? Is this true ? ..............Thanks in advance