Mid cycle spotting, SO confused.

I have been having a lot of strange feelings lately. Last month I was near convinced that I was pregnant. I had sore BBs, occasional nausea (no vomiting) , wild mood swings, a definite widening of my hips(among a plethora of other odd symptoms) ... but a loss of weight.

I should probably mention that my cycle is running 31 days on average and is fairly regular.

I broke down and tested near the end of my cycle. The test came up negative. I got AF a day or two later. It was much shorter and lighter, with no cramping whatsoever. But it was definitely more than spotting.

About a week ago, my husband told me that he thought I was pregnant. He sited my emotions, telling me that he has only ever seen a woman like this once before, and that she was in early pregnancy at the time. So, we went and bought a test... which we took on cycle day 11 or 12. It also came back negative.

Now comes the really strange and confusing bit... Between cycle day 9 and cycle day 14 (July 17-22) I have had what feels like the symptoms of a UTI show up and leave on three separate days. I have gotten rid of the symptoms each time by flushing my system with water.

On cycle day 12 I had just the tiniest bit of spotting on the tissue when I wiped. It was just a touch darker than urine. On cycle day 14 (yesterday) I had a bit of brown spotting. Just BARELY noticeable on the pad, more so on the tissue when I wiped.

It cleared up at the end of the evening, and has not happened at all today.

Does anyone know what this could be? I have scoured the internet and found a lot of possibilities (some frightening and some not) But does anyone know from experience?

I would have suspected implantation, but for the fact that it happened several days *before* I was due to ovulate. For the record, I have never had mid-cycle bleeding before. IE- I never bleed when I ovulate.