3 months since last AF but only getting BFN

I've very discouraged the last few weeks, my last cycle was AUG 26-28 WHEN I missed Sept I didn't think too much of it that's not uncommon as I skip one every few months and it will come by the first weeks end the following month. So mid way through Oct I decided to start testing and got negatives and I've test a few more times as recent as last Friday and still neg I have no signs of my peroid and I have had some early pref systems but not enough consistently. I've giving til the 1st of next month then going for a blood test. We are TTC and have Been for over a year we have a 6 year old and desperately would like to have another. Any good thoughts or helpful advice is welcomed