What is going on?!

Hi ladies, So my partner and I decided we would try for our final baby last month, there was no pressure though because we already have two kids, so if it happened it happened if not that was okay too. But I am now up to day 69 of this cycle, my last period was on the 25/08 and it's now the 01/11, my periods are usually between 32 to 42 day (max) so they are irregular but it has never been this late. Yesterday I started spotting brown (CD68) and today nothing at all. pregnancy test are showing negative. (I've taken atleast 10) but haven't taken one for about 5 days now. I don't have PCOS, my hormones and thyroid are fine (from blood test) and I've never been on birth control. I had an ultrasound to see if I had PCOS 16 days ago, surely if I was pregnant he would have seen something right? Or if he wasn't looking for that would it have been missed so early on? I'm so confused!