You and I have very similar situation and my smell started when I was 14 as well. For a long time I thought its intestine related as well but I'm starting to suspect its more like apocrine gland related. My smell is much worse when I'm stressed which suggest increased gland activity. While certain foods does make me smell worse I'm guessing it's because of the bacteria present in my skin love those bad food.
Notice your smell is better when you're in your house coz you're not stressed and not much apocrine gland secretion.
Unfortunately deodorants and anti perspirant only plug eccrine gland and not apocrine.