4 month old not eating

My 4 month old is breastfed but also drinks pumped milk from a bottle. The past 4 days or so he hasn't been eating well at all. He will breastfeed for 3-5min tops & then he will stiffen up & throw his head back & start thrashing & screaming. He does the same thing w/ a bottle half the time & only eats a couple ounces from it when he does finally eat from the bottle. He was sick w/ a cold 2 weeks ago & was going the same thing but when he got better about a week later, he was eating fine. Now he started doing it again but he had no fever. I took him in & his dr said it may be a sore throat & that's the only thing she could think it might be. I've burped him & given him gas drops & gripe water, nothing has worked. He's also been waking up 3-4 times at night when usually it's only once. He will be 5 months the 25. Anyone else go trough this or have any advice