What Causes Heavy Periods,mild Cramping And Vomiting On Being Diagnosed With PCOS?

I took cephalexin around the 12th of feb until pills ran out. I have pcos and was sexually active during that time. I had a period that was very heavy. Now its a month later and i have mild cramping vomited one day only while eating dinner i felt queesy thinking about the food I was eating. Could I be pregnant even though i tested negative, but since i have irregular periods and pcos its hard to tell.