Sorry long post...

So I need some advice. My LO has suffered from acid reflux from the start. He's 5 months old today. We've been on 3 different formulas and now our 7th YES 7th FORMULA!!! I'm so frustrated as nothing seems to be helping him and his GI issues.. we were on alimentum for 3 months and he just stopped drinking it all together and he's considered underweight, in the 5th percentile. We finally got to a GI specialist and he now is on lactose free formula.. I mentioned he had a couple mucous stringy poops... we tried Elecare and he didn't want it and now we're on Alfamino.... he tolerates it.. but he strains soooo bad to poop and they're rock hard balls when they come out (picture to show) they won't run lactose test to see if he truly does have an issue.. makes me want to go back to a basic formula now that's he's on stronger meds for reflux and see what happens.. I feel like we're just digging this hole so deep for him. He has a swallow test on Friday scheduled to see if anything is going on internally.. also ever since being on lactose free formula he throws up like half his bottle everytime.... any suggestions??;/