What Causes Stool Odor, Urination Frequency With Low Weight?

hello doctor, this is about my baby boy . he is one and half year old. In recent times, his motion smells badly, and he urinates very frequently. he is jus 9 kgs since his nineth month. his food habits are just normal, his diet include fresh fruit juice, pulses, rice, vitamins.Do we need to see a doctor in this case. Kindly suggest