Cramps, fatigue, nausea, irregular periods. Ultrasound shows cystic structure. Meaning of scan?

Hi. My periods have been irregular this year and for the last few months ive been experiencing cramping, fatigue , nausea and some other symptoms. My ladt cycle was 26 days, light bleeding and spotting, this was on 7th July. On the following monday i went to the Dr who sent me for a urine test and ultrasound to rule out pregnancy. I missed the hospital tedt but the scan shoed a cystic like structure that could ne a gestational sac of 3-4 weeks. The following afternoon i fid a hpt which was negative as well as 6 days layer with fmu and it was also megative. My question is what could the ultrasound mean? Im planning to do the hospital scan tomorow and my second scan is this monday. Im still having on-off ovarian type pain, fatigue and sore breasts etc etc.