Pumping to breastfeeding help??

I recently started exclusively pumping because our pediatrician told me that it would be best to just give my then 3.5 month old baby a bottle of formula instead of trying to breastfeed him anymore because he was losing weight and cluster feeding. (We’ve switched pediatricians since then due to other reasons as well, for example I had a feeling he had acid reflux since he was a newborn but the pediatrician practically told me I didn’t know what I was talking about. We switched pediatricians and got him on Zantac and I swear he turned into a different baby. He’s 1000x more happy now) Anyways, we gave him two bottles of soy formula after that visit and he absolutely hated it and wouldn’t drink it. So I would nurse him as much as I could and then I’d pump and feed him a bottle. It was working great but he was nursing less and less and eventually stopped wanting to nurse all together. I think it’s because the milk flows out much faster from the bottle than it does with my breasts and he doesn’t want to wait for the let down. I’ve tried hand expressing first, drawing my nipple out with the breast pump, getting them harder, sandwiching my boobs, everything, but he’s too impatient and gets mad.

Does anyone have any advice on how to get him to nurse again? He just turned four months old