Not sure but my sister is in the exact same boat ( down to last cycle being 26 days, usually 28 and now on cd31, also has a son, are you sure you aren't my sister actually??!!)
She is getting bfns too, will have to wait and see I guess.
Her son has suddenly started refusing to bf which made me suss too, but still getting bfns, weird.

Hope you get one or the other soon!