D.,
Your dr is following advice based on studies showing that exposure to food before 6 months has a dramatically increased risk of diabetes (we are not sure of the link). Plus I don't know your history of your baby's tummy, but some kids tummy's just take longer to mature than others. I waited with both kids till 6 months.
Okay I could be totally wrong, but it sounds like your baby boy has an issue with texture, not food itself. To overcome this sloooooowwww dowwwwwnnn and mix formula with his food (measure the amounts). Give him 1/2 to 1 teaspoon before a certian number of bottles all day every day. Once he starts swallowing work up to 1-2 teaspoons, then to 1/2 a jar once a day,then 2x a day, etc.. At that point decrease the amount of formula mixed with the food, sloooowwwly, like 20% a day (if he will let you)....If not decrease by 10%. Stick with one type of food probably apples (use organic it is consistently sweeter or make your own just steam yellow apples-preferably and peeled ofcourse and mash then add the water you steamed them in (use the microwave). Make sure it is really watery for you baby! Maybe steam in formula (if you can do that-I can't remember). I had to get my daughter to take Nutramigen at 6 months (it tastes terrible,smells terrible)...This is how I managed to do it.....And this is how I managed to get her to eat food it took months to get her to eat real food, but she does. Oh and get the mesh bag thing so when he is ready you can put avocados or bananas in it and let him mash the food with his gums and suck it out. Oh and give him a spoon so he feels more in charge.
Talk to you dr about your concerns, I really think it is a texture thing. Rice cereal will not solve all your problems most likely....
PS--I had to make all my own baby food to get my daughter to eat table food, consistently making it thicker and thicker (but no chunks). I know this sounds like a ton of work, but once your baby likes a type of food you can freeze back a ton of that in a couple of hours--using ice trays-once frozen throw in a freezer bag and label and date.
Hang in there, he is still really little just be consistent and thank God/or whomever that it isn't something much harder to deal with.
I totally understand your concerns. My son didn't eat anything besides apples, pears, carrots and cereal for months (turned out he had silent reflux--heartburn). And my daughter had the texture thing, which even now she hardly eats meat, due to texture. But eats a decent variety.
This will pass!
Rochelle