Implantation rash?

Has anyone heard of implantation rash? I hadn’t but when i called my dr she mentioned an implantation rash? I am 2 days late (no positive text- using cheapies) my dr wants to do a blood test in the morning due to a rash all of my body that I’ve had for about 4 days. Nothing has changed in diet, soaps, laundry, sheets, etc. we can’t think of anything that would cause an allergic reaction. I did a quick Google image search and it looks similar but I’m not convinced.. it’s just tiny red bumps that itch and burn and come and go throughout the day. Worse on boobs and abdomen— any ideas or feedback?