Freaking out

2 weeks ago I took a pregnancy test(8.5 months postpartum and haven't gotten my period yet) and it was a faint positive, so I waited another week, and I took another one, it too was a faint positive. Took a digital, it was negative. That night I started cramping and bleeding, bad, so I went to the doctor and they did a urine test and it too was negative. I was sent for an ultrasound and bloodwork and I got results today. Not pregnant, nor was it a miscarriage. I have a retroverted uterus and a 6cm mass in my uterus. They think the mass could either be left over placenta, a polyp, or a fibroid. I'm freaking out because my aunt required a hysterectomy due to fibroids and polyps that turned into cancer and I don't know what to