I need help please

Ok my lo turned 6 months and started having trouble with constipation he was normal up until 6 months only change I did was start baby purée and literally just barely started like a few taste here and there nothing on a schedule. Ok so I kinda stopped feeding bc he was so backed up and have stopped completely now I talked to his dr and she said “oh it’s ok keep feeding him also some apple juice to get things flowing” she also mentioned doing liquid suppository which I did and it helped him greatly but it only helps for instant relief not like everyday thing so I asked her how often should I use those and she every so many days but I also don’t feel comfortable doing that all the time like won’t I mess him up??? so I had already tried prune juice/purée nothing worked

Then apple juice nothing it doesn’t help and I don’t want to continue giving him added sugar for no reason! What can I do what are some options?? He also seems gassy/bloated and he’s been so fussy. He also does this thing where he bends up and down or scrunches at his belly and then suddenly cries. I did a liquid suppository 2 days ago he went instantly and then the next day nothing then today I would of tried again a suppository but I wasn’t home early enough with him he ended up getting so upset at my moms and he tried and strained himself but he ended up going on his own but he was in pain I felt so bad! He’s just not himself anymore

He’s formal fed ( gerber gentle) and eats 4 oz every feeding

Someone please help me give me suggestions!!!