Help with my Lab

Question
Good Day!
My 11 month old lab doesn't eat well and has constipation. He poops at multiple spots when I walk him (3 times a day).. I notice he tries hard by squatting but can't clear his bowel entirely at once.
Regarding his eating he usually eats just once a day..about a bowl of Dry dog food or rice and some milk. Apart from this and some water, he only keeps chewing his sterilized bone..thats his daily intake. He is slightly avg built.
1) How do I help with his bowel movement?
2) Is this eating little got to do with his constipation?
3) This problem is on for nearly 2 months now and the local vet advised me to include Bananas.. is that ok? something better?
4) He itches a lot despite bathing him once in 2 weeks with antiparasite and oat shampoos. Any advise on this please?

Thank you for your advise in advance. Have a good day.

Answer
I would start out cutting out the rice and milk.  I would not start the bananas.  Stick to the dog food.  One meal is fine at his age.  He may need about 3-4 cups.   Your dog definitely should be narrower at the waist than the hips and chest. You should be able to easily feel the ribs, but not see them. Each dog is different. Standard recommendations are a good place to start, but each dog must have its food and exercise adjusted to its individual needs. Here is a link to a good illustrated guide, http://www.longliveyourdog.com/twoplus/RateYourDog.aspx

Cut out the baths.  Instead, brush him good every day with a soft bristled brush.  If he isn't doing better in a month, I would check with a different vet.