Spotting 8dp5dt

Marissa
I've been having very very light brown spotting today (8 days after a 5 day transfer). My beta is on Monday. Is this normal. I'm worried because I've never had spotting while still on progesterone. Even after stopping progesterone, AF takes forever to come. This is my 3rd FET and I've had 2 mock transfers in addition to that.
Anyone here have any input?