af 16 days late and bfn

Cd 47 af is 16 days late not and only bfn on 4 tested now :( called my doctor and there having me go in for blood work today. Trying not to get my hopes up as they have been broken down now. I'm never this late but I am on thyroid medication and I know this can effect it. Hoping everything works out and even if no bfp comes I at least can get some answers. Anyone else get negative home tests but blood work say otherwise?