What Causes Urge To Urinate And Burning Sensation In Vaginal Area?

Question: Hi,

I had a serie of symptoms in the last several month, that I feel are somehow connected, but I cannot figure out how.

It began at the end of winter, when I had something that felt like a urinary infection. I received an antibiotic treatment, even though they didn't find bacteria in my urine, and the symptoms dissapeared for a while. However, few month later I had again a more frequent need to urinate and a burning sensation in my vaginal and urinary area. All the gynecological tests and urin analysis didn't show anything. Later in XXXXXXX a gynecological ultrasound tevealed that I had larger amount of free fluid in the pouch of XXXXXXX (this was before my ovulation, but I had digrstive issues at the time - diarrhea for several days). The doctor didn't investigate it further.
And now, for more than two weeks, I feel a dull pain and discomfort under my right rib, that radiates in my right shoulder blade and turn into sharp pain when I am in positions where my rib is hitting that spot. I also feel tired and are a little dizzy. I went to my GP, who performed a serie of blood analysis that didn't show anything except a lower ferritin level (11ng/L). I also did an abdominal ultrasound that came back notmal, except that the doctor saw some free fluid in the POD again.
I have to mention that I have a history of digestive issues and was diagnosed with IBS and gastritis.
When I combine these symptoms: pain under right rib + low ferritin + free fluid in the pouch of XXXXXXX + tiredness, I am scared that I might have some cancer, and I am freaking out not knowing the cause.
Do you have any suggestions of what might be causing all this?
Thank you for helping!
XXXXX

So you think the urinary tract infection cannot be cause of the fluid in the POD and the pain, or the opposite way around - can fluid in POD cause urinary discomfort? It is unrelated?
My GP gave me to do a HEMOCULT analysis, to see if there are traces of blood in my stool. I had a gastroscopy in November last year, that just confirmed gastritis. The last colonoscopy I had was in january 2014, so I would need to repeat that.
Can this all be due to endometriosis maybe? My gynecologist didn't mention that, but a lot of my symptoms seem to match, except that I don't have specially painful or excessive menstrual bleedings.