How can this happen?

How can you test positive for ovulation and have sex every other day for three weeks straight and not get pregnant? I have a two year old already with my husband so we know we’re working down there! Taking pre natals, in good health, etc etc.

I just don’t get it. With our daughter, she was not planned but it only took three months! Here we are going on month 5 with no luck.

Any ideas?