Hi there,
I've researched this a lot and found several websites that post timelines....Implantation can take a few days to be fully completed....The first two days after a five day transfer involve hatching and then the next three days after that are when implantation typically happens (according to what I've read). I posted a discussion post with a link to that in the IVF with Donor Eggs support group.
Best wishes & big hug!

Here's the info....

5-Day Transfer
Days Past Transfer (DPT) Embryo Development
One The blastocyst begins to hatch out of its shell
Two blastocyst continues to hatch,begins to attach to the uterus
Three blastocyst attaches deeper, implantation begins
Four Implantation continues
Five Implantation is complete
Six (hCG) starts to enter the blood stream
Seven Fetal development continues and hCG continues to be secreted
Eight Fetal development continues and hCG continues to be secreted
Nine Levels of hCG are now high enough to detect a pregnancy

I had a few drops of brown blood in the underpants at 7 days passed my day3 transfer. The next day I even had a few spots of red blood after a bowel movement (sorry if TMI). I got a BFP on my cycle.

If you are on PIO shots, they generally hold off AF.

So as my doctor tols me: it may be implantation bleeding, it may be nothing, and in no case is it cause for alarm.

I should add, I had taken a HPT that morning and it was negative. The next day it was positive.
Good luck to you.

I'm using endometrin suppositories will they work the same?

I used endometrium with my last pregnancy (ultimately ended in a m/c because there was no sac). The endometrium definitely raised my progesterone and kept me from bleeding.