help, i drink lots and don't urinate

i was wondering if any of you might be able to help me. i usually drink lots of water every day - about 3 litter. but lately i hardly pee and i don't even feel an urge to pee. this really worries me. does anyone know what could cause that?? also, during the day (not neccesarily while urinating, but just during the day) i sometimes for a few seconds feel a burn in my urethra, so maybe it's an infection? can an infection cause me not to pee? but it doesn't burn at all when i pee. it also seems i have a recto-vaginal fistula, and it probably includes the bladder too, that's how i feel it. could it be the cause of me not urinating??

another thing is that although i havn't changed my diet and eat exactly the same, lately i'm gaining weight like crazy - about 1/2 kg-1 kg every day!!! this is totally weird... do y'all think i'm retaining water??

i'm so upset and frustrated, i don't know much about this issue and feel helpless.. i hate going to the dr, cause they would probably won't find anything and tell me to go home.. what do i do? any input or advice will be greatly appreciated, thanks

thanks so much for your reply! no, i don't have edema, thank goodness! the whole thing started suddenly last sunday and went on till yesterday - every day of those days i gained 1/2-1 kg, but since yesterday things seem to be much better again and i started urinating again and already lost 1 kg. i would have expected edema to appear, but although i gained so much, i didn't notice edema on my legs.

i think the reason for this might be b/c i've been eating to much pickls lately    i decided to quit the pickles completely (havn't eaten any since wednesday) and things did get better. so maybe i don't need to see the dr after all?