Fussiness around bed time

I fed my son. He started getting fussy midway through his bottle so I stopped feeding him because he spit up. So I checked his diaper and it was only pee. Then he kept eating at his hands so I tried giving him the rest of his bottle. He did eat the other 2oz but then started getting fussy again. So I made sure I got all the burps out of him and gave him his pacifier to see if he just wanted to suck. I placed him in his swing because that’s what I always do after his bottles since he does have reflux. Then he got fussy yet again so I picked him up and tried again to see if he had burps stuck.

My question is... can babies cry just to cry? It scares me about his feedings because he was losing weight when I was only giving him 2oz. Once bumping it up to 4 (pediatrician wanted him on 4 to see if he could gain his birth weight back) he was way more content.

I cleared the mucus out of his nose and he was still fussy after that. I have a heartbeat noise on and rubbed his head while he fell asleep but we’ll see how long he actually stays asleep.