Some darkening of the groin area is normal because the increased hormones in the area can cause some color change. The spots and "stickiness" you are describing may be a fungal infection. These infections like areas that are moist and warm. It may be reasonable to try some of the over the counter "jock-itch" creams to see if this helps some. Inflammation from these infections can also lead to darkening of the skin.
I would recommend you have this evaluated by your doctor when you are in next.
Advice and opinions given are based on the information provided and must not be considered an official medical recommendation. The limitations of the internet prevent an appropriate evaluation. Always consult your doctor if there is concern.