Two obvious possible reasons for this, both of which require a visit to a doctor
1) Thirst and frequent urination can be a symptom of high blood sugar. Do you know what your levels are like?
2) Prostate issues are common in males as they get older, and there's no need to suffer them in silence.
Of course, there may be another reason altogether, but I suggest you get checked out.
Good luck, and welcome to the forums.