5dt 11dpt horrible cramping

I've had light cramping on and off since the transfer. last night I got woken up by terrible cramping and couldn't go back to sleep. after awhile it would subside and I could finally go to sleep. happened again. this morning I went to bathroom and I noticed I had light pinkish/brownish bleeding. It's been that way off and on today. Just mild cramping during the day, nothing like how it was last night. I've been going to the bathroom more, I'm tired today and have a headache. Could the strong cramping be from implantation? And has anyone else had this happened to them?