I've been spotting for 2 weeks

Can anyone relate? 
A panty liner is all I've been using throughout these past few weeks.
There are days that I only notice it when I wipe. 
Other days is a step above light spotting with some blood clots (I think that's what it is?)
But overall, it's mainly spotting. 
I have taken a couple of at home pregnancy tests and one at the doctors. They all turned out negative. 
Last month I had similar spotting but didn't last as long, it lasted one week. Both came a week before my expected period.
I have an upcoming doctors appointment in a couple of weeks. I can't wait, I'm so over this! I need answers. 
If this is of any help, I've been off birth control pills since Nov. 27, 2014 (4+ months) and have been trying to convince ever since.
Any comments/thoughts are greatly appreciated!