5 month old not eating enough and slow weight gain -HELP

[HotI]

I don't know about long term solutions, but i would be worried about trying to give him some formula right now. Have you tried using a teaspoon and giving him formula that way? You can also try cup feeding- a shot glass or small medicine cup works well for little bubs.

here is some info on cup feeding (its about half way down the page) Australian Breastfeeding Association - Cup-feeding

Did you have difficulty breastfeeding? If he has a tonguetie or similar that made breastfeeding difficult it might also be making bottlefeeding uncomfortable for him. Just an idea. Do you have a mchn you like that you can talk to?

[Arimeh]

Sounds like he may be teething? My kids did this when their gums were hurting. I rubbed some SM33 on their gums, and then they would feed properly.