Thank you guys for you help and good advice !
Yes, you should see a doctor. do you take meds for your nerves? there's all kinds of things this could be. After you get a check up you could narrow down if not fix the problem. It could be your prostate or you could have a food alergy, even if you haven't eaten anything out of the ordinary, you could have developed one. You could try process of elimination. Start with foods that are commonly pin pointed like spicy and greazy or dairy products or it could also be malnutrition. Espeasially if you are having diaria constantly. you can become dehydrated and enimic.
it is a normal sensation to feel the pocket after you pee if you hold your pee for long times
since a small amount of it remains in bladder,in addition some is still present in your ureters when bladder got full.
and sure it is not the prostate as suggested by kev.
seems he forgot that you are female
wish you get better soon