Hello Customer (name blocked for privacy),
Implantation bleeding is usually accompanied by cramps but not really a bad cramp. Such bleeding is usually noticed almost on the same time around an expected period but the bleeding is usually very light just enough to soak a panty liner which usually lasts for a day.
If you are expecting your period at this time, wait and check on the bleeding - that usually would differentiate the menstrual bleeding from implantation bleeding.
If you had a missed a period and have that symptoms, better to do pregnancy test as those symptoms are sometimes early manifestations of an ectopic pregnancy.
Take care!