Unless she (the U/S person) has had a cyst herself, what does she know about the way they make a person feel.
I had all the symptoms you just described when I had a cyst with the possible exception of the nausea. Pain came and went, especially at night or after a bigger meal, and it traveled down the legs. When it hurt that bad, sleep was impossible until Ibuprofen dulled it for me and thankfully a small dosage was enough to work.
Cysts can press on the bowels so what she thinks is a bowel condition could easily still be the cyst. Unless you have other health conditions you didn't mention, the cyst could be the cause of all your misery. I know mine was.
Did the doctor talk with you at all or just the U/S person? Normally U/S results are sent to someone like a radiologist (first) to read it and then to the doctor to explain it to you. Normally you wait a few days to know the facts, including the measurements. Then hopefully you'll get some answers on how to treat it and get some relief.
I'm very curious to hear what type of cyst and what size. That will make a big difference in how it will be treated. Yes, I had all those pains and it can also be referred to other areas.