SO CONFUSED

Please help. I usually have a 27-29 day cycle. for the last 8 months, I have started spotting three days before AF and then the flood gates open. I also usually have really awful skin. This month, I am currently on CD 31 and this is my 4th day of super light spotting. I just worked a 12 hour shift and only have a teeny bit of brown blood on my pad. I have been cramping for 5 days. And it's not like normal AF cramps, it's like a burning cramp. And for the last week, my skin has been miraculously clear and I have never been so tired in my whole life. Sounds like I might be pregnant right? No. Every single pregnancy test I've taken is so negative. Does anyone have any advice or thoughts??