I think my son is lactose what do I do

3👼🌈💖2018🌈💙2020💖2021💙2023 • God's timing is perfect🙏⛪

So I ate a bowl of ice cream with my daughter yesterday and since then my son's throwing up has been excessive he has thrown up since birth and me and his doctor are in the middle of trying to find out what is wrong with him he prescribed him a certain kind of formula which is Similac Alimentum and my son will not drink it and I do not blame him hit smells and tastes sour anyways I want to ebf but it is hard because my son always wants to eat and I'm afraid I am not producing enough for him right now I don't want to breastfeed him much because he is throwing up like crazy but he is also doing the same thing with formula I have try the purple can of Enfamil I have tried AR and I tried ProSobee I do not feel comfortable giving my son the one prescribed by his doctor because he don't go past a half ounce before he is crying and trying his best to get the bottle out of his mouth I don't know what to do I'm at my Wit's End I exclusively breastfed my daughter and had no problems like this with my son I am going crazy and do not know how to handle this situation poor thing does not keep a single feed down and it does not come out as spit up it comes out pretty forcefully can someone prescribed a formula that is similar to the Similac aluminium so we can figure out how to help him feel better thank you