If it is urine there are two possibilities how it can leak - one is overflow incontinence - in this case the bladder is always filled with urine and when the volume of the urine exceeds the volume of the bladder - there is leakage of the excess urine. This occurs without the knowledge of the person depending up on the water intake and urine production.
Second is leakage of the urine through an abnormal pathway. There may be connection between the urinary system and vagina or the uterus. In such case the urine from the either ureter or the bladder escapes through the connection into the vagina or the uterus -which eventually leaks outside like menstruation.
Only a clinical exam and imaging scans will confirm the diagnosis of this kind of leaks.
Vaginal discharge can also cause this but will never smell of urine.
As you suspect it could be excessive sweating too.
What ever a problem might be,it is never embarrassing to see a doctor to discuss your problems.It could be a medical issue which needs prompt attention.So earlier the better.
You can use talc powders and antiperspirant to see if it helps.
But the best way out of this situation would be to see a doctor as early as possible.
If you have any more questions ,please let me know.