I had heavy bleeding w heavy cramps for 2 days and the bleeding died down for the next 3 days, one week after plan b. was this implantation or period?

Late periods: It depends on how old you are or if you have had intercourse within the "danger" period, but check another pregnancy test in 1 week to be sure. Irregular potting indicates hormonal imbalance which may be natural as you age, or related to a number of other factors, most likely from plan B in your case. Recommend you visit an MD clinic to be checked out.