Hi there,
You have said nothing about his development, other than his wieght, which is FINE. Has he hit is developmental milestones, ie. is he rolling, sitting independently, creeping or crawling, even pulling to stand? Is he babbling? Is he trying to hold or pick up finger foods such as cheerios?? (you didn't mention how much baby food he is eating... babies at this age often get bored with the bottle and are getting more interested in baby food or even finger foods- although you did say he wasn't interested in this either). Have you tried a sippy cup yet?? I know my niece was always difficult to bottle feed... she did much better when she started the sippy cup. As a guideline, at 9 mos, my children were getting baby food at breakfast and dinner time (cereal and a fruit or veggie), and sometimes a yo baby yogurt at lunch time/or more baby food, and 4 bottles per day (about 6-7 oz. per bottle). I would usually mix the baby food cereal at morning and night with formula or breast milk. However, it is not too early to start using a sippy cup to get more formula/breast milk...
What concerns my most is that your child seems to be sleeping excessively and has little motivation to eat (drink). Babies at this age will go through phases (periods of time when they might be teething, more interested in the world around them to eat), but generally show interest in eating and drinking. If he has hit his developmental milestones, I would not worry too much. However, if he is not moving around (creeping, trying to crawl, reaching for toys, trying to clap, sitting independently or with little support) and babbling, lauging etc., I would be more concerned. I am an Occupational Therapist who has worked with young children with a variety of Special Needs. Please feel free to contact me if you have any more specific questions. I feel like I didn't get a lot of other background info from your request.