Pregnant or not pregnant?

My hubby and I have tried for more than a year but got nothing. My period usually very on time. It should due on 28 Oct but so far it hasn't show up. Usually before the first day of period, I could see a little brown color on panties but this month I didn't see anything yet!! Felt like it would come any time, but it never did! I have done three tests all neg... Now I am struggling to do another one as I worried to see another neg...