Aagh! Don't put the cereal with the formula in the bottle!!!! No no no!! I'm not sure if your pediatrician told you to do that, but no! There is no reason to and no need to. Just mix the cereal with the formula and mix it in a bowl and then serve it to him.
You should always start slowly when it comes to food. You have a good system down, but remember the 4 day rule. Introduce each new food for 4 days and then try another and then wait four days and try another etc. Once they get use to the different foods and textures, you can determine if he is allergic to any types of food. Then you can mix and match the peas and the carrots and then fruits once you know he's not allergic to an individual item. There is also a suggested guideline to what foods to feed first before you start giving him meats and such. The website I suggest later will help you with what to serve when!!
Always start with formula first...that is where he gets his most nutrients from, not the food right now. Then offer the food. Food is good, but he's still developing, you're weaning him as we speak off of the bottle. Anything you put in your baby, instead of the breast or formula, is in itself weaning. You're obviously doing it very slowly and gradually, but you are getting him use to other ideas of other things instead of a bottle. (A lactation nurse told me that once!)
Anyway, if I were you...I would:
Start with a bottle in the morning....wait a bit see how he is doing, play with him, then offer some cereal mixed with formula or fruit, or just offer fruit in the morning.
Play some more, nap, do you thing..
You don't have to give him three meals a day at once, start slowly, start with one meal, then two and then move on to three meals a day and even introduce snacks in there too!
Then around "lunch" time you can give him a vegetable followed by some fruit if he's still hungry, but always the Bottle FIRST!!! (maybe sure you introduce each first before mixing and pairing - allergies!)
Same thing around dinner time.
You'll start pacing your bottles out more and more, but he should still be getting the same amount of formula across the day. Ask the pediatrician how much formula is to be taken in for a 7 month old. I nursed both of mine, so I don't know exactly the amount of milk they are to have each day. Mine nursed great and took in what they needed each day, so it's unsure exactly how much they took in.
Then you can reevaluate everything again at a year, if you choose to wean him.
As long as he is getting enough nutrients and growing and having a good time, then no worries, but I highly suggest this website for lots of food ideas, combinations and neat info about babies and feedings!!
Go to http://www.wholesomebabyfood.com/
OH!! Just read something about juice....you don't have to introduce juice now...he's doing fine with formula, if you do introduce juice, then introduce in slowly and very little. Gerber makes little juices but I would still water it down big time!! Sugar is not good for their developing teeth and nutrition, so have him get use to a sippy cup with water instead. Water as we know is healthy for everyone!!
Hope that helps!
A. B