Chronic pelvic pain and spotting between periods

So this has been going on for about 4 months. My periods are still kind of normal, but have been getting shorter in length. I've been on hormonal birth control for about 6 years to regulate my PCOS symptoms. I'm very good about taking my pill on time, usually within and hour or two.

1st month was pelvic pain and spotting between periods that lasted several weeks.
2nd month I had no pelvic pain, and no spotting
3rd month I had pelvic pain but no spotting; the pain continued during my next period as well, but lessened as my period ended.
4th month I had just pelvic pain for about a week after, then the spotting started up again. Last night in particular I had a large amount of spotting.
(The pain occurs a majority of the time between periods)

I went to the doctor for it a couple of weeks ago, all my blood and urine tests came up negative for infections, or other irregularities. I also had about 4 pregnancy tests that were also negative. She even went so far to have an ultrasound done, and everything came back normal as well. She told me to just "wait it out," and I'm a little pissed about this.

I'm concerned because from my understanding that when there's pain and spotting, there's a problem. Does anyone possibly know what might be causing this? Has anyone else experienced something like this? Also what other symptoms did you have?