Solids wont necessarily make him any fuller, he may just be a hungry baby. I would personally stick to just breast milk/formula until 4 months. 3 months seems awfully early.
I tried at 4 months and he has no idea what to do with it, would thrust it out every time so I let it go.
Tried again at 5 months and he did much better.
I started with rice cereal, with formula very runny and only 2 or 3 bites.
I also did it every other day to gradually get his belly used to it.
By 5.5 months he was eating like a champ so I started offering it daily.
A week before he turned 6 months I started to offer veggies.
If you plan to follow the "AAP Rules" also make sure your child watches NO television until 2 years of age, does not use a walker, and does not use a swing until 6 months of age, no longer than 30 minutes 2 times a day.
Because the AAP also believes in all that garbage.
Good luck
