Ideas on what's going on with my DS?

Hi Ladies. My DS turned 1 month on Nov. 2. For the last 3+ weeks, he often screams/grunts during his bottles and then chokes a little on the milk from all the straining. It's so sad how he screams and cries. He has also been having problems having a bowel movement. He struggles and grunts so much and he is very gassy. Sometimes he can go on his own and sometimes we take his temp, which almost always works.

During those times, the first part of the poop to come out is pretty firm/pasty, but afterwards, he will go a ton and it will be pretty loose/runny. When he does his crying/grunting/screaming during his bottle, I will go and take his temp, he will poop and then can take the rest of his bottle without a problem. This is almost always the case, but he has done the screaming during the bottle after a smaller poop a few times, which now makes me wonder if the poop thing and screaming during bottle are always related.

He does spit up but not all the time. Every 3-4 days he will have a huge spit up, maybe even what would be considered vomiting, but it's not projectile. It does come out of his nose sometimes.

We have taken him to the pedi several times and he said this is just his instestines learning and something he should grow out of. He has us giving him apple prune juice, 1 oz, morning and night, which does help. We have him on Target Up & Up's equivalent of Gentlease and the pedi said this formula is fine and not to switch. 

I am just so tired of seeing my sweet baby suffer.  Any ideas?

TIA.