I mean that is DEFINITELY a line. I would say without a doubt if that were urine but I'm not sure about it being breast milk, if it means the same. I would imagine so! Trying to think of why breast milk hCG concentration would be higher than urine tho...
Okay did some reading and I was wrong (Edited my post), at least some substances like alcohol are in the same concentration in breast milk as they are in the blood. So, the question is, is hCG one of those substances?
So my explanation: you are really pregnant, but just super early, and your breast milk is showing your BFP because blood concentration of hCG is always higher than urine concentration of hCG (which is why pregnancy can be picked up on a blood test before it can by POAS)