Sulfamethoxazole and lungs

I have been taking this medicine for a UTI for a few days and today all of the sudden I had an uncontrollable need to pee every few minutes. When I did there was a burning sensation and the immediate need to pee again. So I looked up the medication and saw online that you are supposed to drink a whole glass of water with each pill. I started chugging water and the burning and need to pee went away after and hour or so. Very strange, but maybe it will help someone else.

My husband is taking this medication to clear up little infections in pockets in his lungs caused by scarring. He has only been taking this medication for about 3 days now but has complained about cramping in his legs. This is not listed in the side effects, but I see that others have had this same symptom while on this medication. I am not sure if this side affect goes away or if this is a reason to stop taking this medication. Anyone out there know about this side effect?
Thanks,

Sulfameth was prescribed to me for UTI. After taking 2, doses i started itching all over specially between my skin folds, too bad i have to work 12 long hours but so far managed to endure the itching. I was a compliant pt so i continued taking the pill, on my 6th dose, i noticed that all of a sudden i started coughing. It seemed that my lungs were congested, now i am thinking there is probably fluid retention in my lungs... i have 7 more days to complete the dose...hmmp... i don't have to be compliant this time!