Could I be pregnant?

Me and my SO are trying for baby number 3. I haven't had a period sense July,29,2017. but i had to periods in July . the first one on July 2 threw July 8th and the second period was july 29 to July 31 . so i took 4 pregnancy test and they all have come back negative. My periods are irregular but I have never gone this long without a period . Idk if I'm going crazy or what . Could I be pregnant??