Spotting is very common after transfer and durin the 2ww. It can happen at any time and range from brownish to red. It can be from the manipulation of the catheter to implantation. Remember your endometrial lining is thick. Of course, if you saturate a pad call your doctor. And yes, I see a lot of BFP's!!!!
I am an infertility nurse and I work in a major IVF facility. I am willing to answer questions and give guidance, however, since I am not treating you, only your physician can give you the most accurate information.