Another Negative Test...

I am two days from my expected period and I am getting a negative on the first-response test. Ive been nauseous today and I have been so tired all week. Ive had a backache. I am having similiar symptoms to when I concieved with my first LO. Last time I was testing positive by now. Feeling discouraged. Any other second time moms have experience? My daughter is 6 months old and (I know we sound crazy) but we have been trying since I had my first period. Ive been tracking and still no luck.