Quoting elle-marisha:" He wanted it. It fills him up. He is happy. And he is still breast fed. Do you mind just being happy that he is happy?"
It doesn't give him any nutrients that breastmilk doesn't and the digestion of a 3 1/2 month old is not ready for regular food. Your basically filling him up uselessly. If he's still hungry, feed him more breastmilk - ALL babies show interest in table foods, your putting something in your mouth and he's curious - that doesn't mean his body is ready to digest that stuff or that it gives him anything that breastmilk doesn't provide.