So, should I see a doctor? I drink but have decreased urination.

Factor sweat/weight. If you drink more than your urine output but your weight is stable then you are losing the difference some other way e.g. Sweating much, excercise, diarrhea. Occ, you don't notice sweat but are always staying warm i.e. Low level of a/c. Also, possible that you don't urinate frequently but each void is large enough to remove intake. If wt is up or have swelling, see a doc.