I Been Taking Metformin The Last Few Months My Periods

I been taking metformin the last few months my periods started on the 14th than started coming on the 4th well on the 4th I was expecting a period and no period my boobs hurt I'm very emotional and I had cramps like I was going to start a period so I waited til the 14th and still no period my boobs still hurt what can cause me to miss my period besides being pregnant and I haven't took a test yet