Just looking for some feedback.....?

OK here the situation.......I am more tired lately, but I do have a 1 yr old who is learning to walk. I am two weeks late, and I am pretty on the date when it comes to that. My husband had a vasectomy about 8 mo ago, and I took 2 pregnancy tests that came back negative. Just wondering if anyone had any feedback on what migh be causing all this. Of course my 1st thought was that I was pregnant again, but with the neg readings and a fixed husband, kinda ruled that out.