Your story sounds so similar to mine! 2 years ago, I experienced severe bloating, pain in my lower abdomen and more frequent urination. I also had constipation and digestive issues. After ruling out any major bowel issues with my doctor and no relief from laxatives, I ended up in the ER with pretty bad pain. The CT showed a large 11 cm cyst. It was thought to be a complex cyst, not a simple functional one. I consulted with an OB/GYN the next week, had bloodwork and a repeat ultrasound a few weeks later. The cyst had not changed and I was scheduled to have it removed the following week.
How large is your cyst? From my experience, if they are over 5-7 cm and expecially if they are causing pain, surgery is usually presented as an option. Often, they will recommend watchful waiting. If you are having this much pain, I feel pretty strongly that they should repeat the ultrasound to check to see if it will resolve or if it is growing. I would definetly ask for another ultrasound. I would honeslty probably seek out another opinion.
As far as the Intersitial Cystitis, I have been diagnosed with this so I am familiar with it, but to me your symptoms sound more related to the cyst. Large cysts can put pressure on the bladder and cause frequent urination. I had this with my large cyst and it went away after it was removed (the IC diagnosis came later). If it were me, I would probably focus more on the cyst, then seek out a diagnosis for the IC if the badder problems persist after the cyst is resolved.
I also wanted to note that I currently have a smaller cyst which is also causing me a lot of pain. It was 3 cm (so pretty small) in January, but my doctor wanted to follow it becuase it was painful. My follow up is Monday. She said we would discuss surgery if it is still causing me pain, even if it had not grown. So, in general, I think the standard is to follow up on cysts, especially if they are bigger or painful.
Good luck! Keep me posted!