What could this be?

Last full period started October 16th for 4 days. Spotted for 3 days in the beginning of December, so if that was just a light period then I’m on CD 55🤷🏻‍♀️ I’ve always had 28-32 day cycles... Yes I’m sexually active, yes it’s unprotected, and yes I know I could get pregnant. I took a test the other day (it’s been 3 weeks since we last had sex), it was negative. Now I’ve been having this discharge for about a week , stomach cramps, my back has hurt all week, sleeping at my job😂, and I actually have an appetite, I usually don’t eat much.

How ever if my test is negative, and I’m not pregnant, what else could be going on?? I just want some opinions from you ladies, I’m going to the doctor Wednesday