How do I get my breastfed son to take a bottle

My son is 4 months old and only weighs 11 lbs. He was born a day after his due date. He weighed 6 lbs 4 oz. When we left the hospital he weighed 5 lbs 14 oz. He has reached all of his milestones, he just isn't gaining enough weight. He has been breastfed since birth. His doctor is very concerned about his weight. His doctor said to feed him every two hours on the breast and add in a couple bottle feedings through out the day. I've been trying to introduce the bottle since he was 3 1/2 months old. He won't take the bottle with only breast milk, with breast milk with a tiny bit of formula, or straight formula. I've tried up to 7 different nipples and bottles. I've tried syringe feeding him, spoon feeding him, and even feeding him out of a medicine spoon. I've tried feeding him out of the bottle before the breast and he still isn't having it. All he does is scream. He hates it. It takes me literally an hour to get him to drink 2 oz. I hate seeing him so upset. I feel like I'm failing him. I need some advice....