Umm I think its kinda when the egg is fertislised but it doesn't stick or something? Don't quote me I only heard of it myself the other day!
I would understand that though if my tests were BFP and then BFNs. I think Im confused because they are all mixed up!!
A chemical is when your egg gets fertilized but does not fully implant in the uterus enough to "stick". You still have trace amounts of hcg in your system and test positive on some tests. Its most often found when women test before their af is actually late. Usually the chemical pregnancy ends within a week of when the womans period should have started. So women who do not test simply usually think their cycle was late and are none the wiser about having been pregnant.
Women who test early on and see the bfp know they are pregnant then test again and may see a bfn. Mine went back and forth it was sooooo confusing and I was so frustrated at the situation!. On the day I was due with my period i had a blood draw and my hcg was only a level 13... so it was waaaaaay low. The next day i started spotting and the day after full blown bleeding.