The female body produces fluids and it's perfectly normal. When it's a problem it can be from an STD, but more often it's from not washing hands or showering or not using good hygeine during sex. This is often a yeast infection or bacterial vaginosis. When you have one of these, your viscosity is poor and sex is uncomfortable and your tissues get itchy and inflamed and there is a smell. Then you have to see a doctor to clear it up.
Normal fluids do not smell bad, but they can vary in color and consistency, but viscosity is good.