Peanut allergy or stomach bug?

So yesterday my 9 month old had a piece of pb&j (for the second time in his life) yesterday around 12:30 and within 5 min started vomiting. Since then every food Iv tried to feed him he threw up except crackers and toast but was fussy with toast. After googling I thought peanut allergy. But he had no hives or swelling that I noticed. Took him to the dr this morning after he threw up his breakfast and he thinks it’s an “upset stomach”. He is a good eater eats anything given to him and then some. So to have an “upset stomach” over mixing pb&j doesn’t make sense to me. He’s had no fever no other signs as if it’s a bug. Is happy playful jumping strong laughing it’s just when he eats he pukes. Had any mommas had a baby with an allergy that just had vomiting with no other symptoms? I pushed the dr saying I’m not comfortable giving peanut butter after that reaction and he said okay we will do a blood test that I set him up later today for. Praying that gives us some answers.