Waiting for diagnosis and worried

I'm 27 and have been having concerning symptoms for several months that doctors think might be ovarian cancer. I'm waiting for my CA125 results, but I would appreciate hearing if anyone else had similar symptoms that led to their diagnosis. It's been a stressful process getting to the bottom of what's going on, especially during COVID, so I truly appreciate this community and your support. 

Starting two and a half months ago, out of the blue I started feeling distention and pressure in my lower abdomen-it feels like I'm laying on a balloon when I'm on my stomach. I also started having GI symptoms including daily acid reflux, constipation, bloating, as well as frequent urination. Daily fiber supplements and probiotics eventually helped with constipation, but didn't help any other symptoms. Eventually the frequent urination and urinary urgency became much worse and didn't improve after being treated for a presumed UTI. The urine culture came back negative for bacteria, and follow-up tests of metabolic function, thyroid, and other urine abnormalities were also negative although I did have low vitamin D. At this point the abdominal swelling became even more pronounced and I was up 2 pant sizes even though I was losing some weight (about 3lb in the last month) and was noticeably losing fat in other areas of my body including going down a bra size. I also started having both sharp pain and muscle spasm-like pain in my abdomen, especially on the left side. Recently, I've also had a very small appetite and get full very quickly after starting to eat, which I'm sure is partially responsible for continuing to lose weight. 

My general doctor referred me to the OBGYN to follow up, and thankfully they saw me even though they were only seeing current obstetric clients because of COVID. I had an ultrasound and they found a 3cm complex cyst on my left ovary. The doctor said my uterus seemed fine in the ultrasound, but it was enlarged when she examined it. She seemed quite concerned by this but didn't really explain why. I would guess this is the lower abdomen distention I've been feeling, but it still seems surprising that and the small cyst alone would cause my abdomen to be so large. The doctor seemed confused both that the uterine distension didn't show up in the ultrasound and that such a small cyst would cause that and the uterine distention and other symptoms I've been experiencing. 

It's frustrating that I still have more questions than answers at this point. Currently, my doctor decided to wait for the CA125 results and have a follow-up ultrasound in a month to see if there have been any changes. At first she had wanted to put me on a different birth control pill with a higher level of estrogen, but after feeling how distended my uterus was, she decided to follow-up more quickly but not start any medical interventions (again, I didn't get much explanation of her reasoning). Also knowing that CA125 tests have so many false negatives, I'm concerned that if it's negative, she'll just want to continue monitoring the cyst without intervening even though my symptoms have been so impairing.

I'd appreciate hearing about any similar experiences or any advice you have for what helped you get answers. Thanks in advance!