What Causes Vaginal Spotting Before A Menstrual Period?

Hello, I'm a 24 year old female and I've never had kids or been pregnant. When I was 16 I started taking birth control pills because I had extremely painful menstrual cramps and my mom thought the pill would help. It helped and I took various brands of "the pill" pretty continuously up until November of last year. I was on Trinessa for 10 months but it caused horrible moodiness and depression. I finally quit taking the pill last November and within a week started to notice myself returning back to normal. So my question... after 6 months my menstrual cycle still seems out of whack. My periods are on time but about a week before I get my period I start spotting, and it lasts all the way up until the real thing starts. This time I've even started spotting a week and a half before I'm due to get my period. It's frustrating because half of the month I am bleeding to some extent. What could be causing my spotting and what can I do about it? I don't want to ever take hormonal bc ever again.