I order a 4 shot latte. I can handle 6 shots fine.
You are either a low responder to caffeine or the beans being used are no good.
I have my own barista setup in my house, paid the guy who usually made my coffee each day to come to my house, set it up and teach me. Once you dial in the shot it’s all about the milk.
Many shops don’t use high caffeinated beans, they’ll do a single shot instead of a double sometimes. I buy my beans from the cafes I go to and the coffee I make at home is almost always stronger (double shot). Family who come to my house for a coffee always comment how strong mine are compared to the shops (they love it mind you).
You’re a big guy so it’ll take more but 4 shots of proper strong coffee would have you racing like a mofo.
Have you tried Lebanese coffee? Shit is insane!