Third time in a row my period is late but it is longer this time, preg tests all say negative?

My period in October was 5 days late, my period in December was 12 days late, my next period should have been, on a 28 day cycle which until now I was like clockwork, on new years day, but I never got it. So that period is now 32 days late. All pregnancy tests say negative including a pee test at the doctors about a month ago and a few at home ones since then. My , not tissue just nipple tips, are sore as of about a week ago, and I don't have cramps but I can feel a sensation down there as of a week ago like a period wants to start but hasn't. I do feel a bit tired lately. I just got out of the military a few weeks ago and so life is great, that was a little stress but not too much really and I really don't have any stress now. I am going to go back to the doctors next week (hubby failed on the insurance thing, he is military too so I have to wait till he come home to do that, he is gone till Thurs.) and see what they say. I am 30 yrs old and not on birth control, I haven't taken the pill in over a year. We did try to get pregnant but nothing. I am not stressing or hoping either way I am or am not pregnant. I went on a two week relaxing vacation and thought it would come then but it didn't. What does it sound like to you? Thyroid? Pre-menopausal? What is this?