sorry, been out all day. i did try on and off from about 4mths to try and get him to take a bottle. like you, he took one fine as a small baby, but i stopped as had too much milk as it was. i always demand fed, but it got to a point when on solids where he wouldn't demand so i would offer as it seemed he wasn't drinking a lot. i was giving him a bf at 7am, 11am and then leaving it till 3pm before another feed when i would try a bottle (he would have water in beaker in between, though not too good at drinking that either). for a week, i tried this (when he was 10 mths) and some days he would take 1 ounce, some days just cry. he screamed and took nothing 2 days running (i always caved in after 10 mins or so and bf him). i was about to give up AGAIN, but the next day he did drink the whole 4 ounces of it. and the next day! i was SO EXCITED!
2 of my friends had similar probs. one did the same thing, battled for a weekend when her ds was 6 mths, then on the Monday he took it and she stopped bf overnight. the other just kept trying on and off and her baby took it from the 'boob bottle' (from her mil) and finally took it from her and progressed to normal bottles (at about 8 mths). so i guess everyone has a different story. another friend can't get her baby to do bottles, and she has gone onto beakers as she drinks quite well from a beaker. another is just bfing morning and eve (as she works) and the baby gets water and yoghurts at nursery (baby is 7 mths), as well as formula in her food.
my ds put on one ounce between 8 and 10 mths, and i was convinced it was because he was not getting enough milk as he is not really bothered about drinking. sure enough once i got him to bottles, he is still only on two thirds of recommended daily amount, but is putting weight on again because it is easier to measure. sorry for long post, but just to know you are not alone.
i am 100% behind bfing and did it for 1 yr despite a lot of problems. but the BIG SECRET is that if you exclusively bf it is a fight to get them to take bottles which for one reason or another (eg. going to back to work, or want to go out and leave baby with your mum/ dh). now i always recommend people to give one bottle a day (and not to stop) even though it is hassle, it will be less hassle later. 2 friends have younger babies than me and have done this, bf fine and transition to bottles been a lot easier. i will do this next time!!! good luck. i know it is hard, as it is difficult to go out and leave them for more than a couple of hours. hope something works in the end...