Feeding difficulty in 3 months old baby.

112 days old male baby .He is active and not asking for feed . Breastfeeding till now.but past one week he didn't feed well .playing and seeing the surroundings.it seems my milk  reduced because he is not fed well for the past 7 days .when I express after feed it is 10 or 15 ml.. he is not crying for feed but urine count reduced to 6 to 8 times but he usually urinates above 12 times in a day.so I thought milk is insufficient and gave formula but he refusing to drink that formula milk .I am very much worried about his health .he is not effectively sucking which is affecting my milk supply and  his weight is 5750 grams in   107 days  and I checked 5 days later ( today ) he is 5820 grams ..Night time he is sleeping 6 hours at a stretch .. There are lot of questions in my mind ...How will I maintain my milk supply ? To make him drink formula I have to stop breast feed because he is not accepting formula after breast feed which is not adequate for him .please help me to find solution?