Hello and welcome to HCM,
Thank you for your query.
It would have helped to know which diet pill
you are taking. If you wish to discuss this further you could write back to me for a detailed discussion.
Most of the over-the-counter diet pills available have some amount of diuretics (drugs that increase the clearance and production of urine) in them. This could have resulted in the increased urination.
Increased exercise and a low-calorie diet in a person on a weight loss
program also lead to an increased urine production.
Although this could result in some amount of weight loss, it is not generally considered a healthy way to lose weight unless you are over weight.
It would also help to know your age and sex, as an increased urge to urinate is a symptom of conditions like prostatomegaly
For now, please consume an increased amount of fluid (water will do), if there is no underlying condition, then your symptoms should subside soon.
I hope I have succeeded in answering your questions, you could write back to me anytime for further clarifications.