Random spotting between periods?

I started my period on the 19th like normal this month, but it was extremely light and after the 21st was only light spotting randomly before it stopped completely two days later. I've never been very affected by my period except for cramps which I also didn't really have this month. I took a pregnancy test to make sure I'm not in fact pregnant on the 23rd, but it came back negative. Tonight, I went to the restroom and found I am spotting again. It's a pinkish color and is mixed with cervical mucus, and I again haven't been cramping. I have been extremely tired and moody for the past two weeks, also. My fiance and I have sex regularly, but only some times remember to use a condom. He always pulls out. (Yes, I know we should remember every time) Thank you!