hey i think i know why! i have the same exact problem!!! when im at the mall with my friends i act really hyper but i dont feel anxiety and i tend to be really fun around them. but if im hanging out with my parents, or no one at all, i get really nervous (my mom is really eccentric and i hate my dad) and i get alot of stares at the mall.
and i do get very stoic and unemotional-like when im anxious (i get the tired eye bruises), and like i just want to leave the mall cuz everything hates me and is out to get me. but this may be cuz i get extremely exhausted by social situations.
anyways i did some research on this bizarre social impediment and well, Asperger Syndrome came up. its like a minor form of autism, except while autistic people dont care about social situations, aspergers tend to WANT to be social (most fail at it, we're both lucky we have friends that accept us).
what the asperger thingy does to some people is it makes you alot more "tired"->(from being anxious) in social situations than other people (even with friends sometimes), and you also tend to worry alot about... well everything in general.
also, ive noticed that i get these urges kind of like ticks when im in these situations that causes me to "raise my body defenses" i guess. for example, i have my hands in my pockets, i slouch, my eyes dart frantically around the room to make sure nobody is laughing at me. people always tell me i that i look like im afraid that they're going to hit me.
regardless of if either one of us do has this so called "aspergers" or not:
what i realized is that you actually can control these insecurities by acting chill such as: constantly telling yourself (in your mind) not to worry, that you can blend in with the crowd well, relaxing your muscles, and straightening yourself out when you go to little break rooms such as the restroom or in the changing rooms.
but the best way to deter from these anxious situations is by trying to avoid going with your parents (in the mall), and instead going more often with your (close and talkative) friends.
also, talking about your problems to your friends (in person) helps alot cuz they wont leave you if they understand. but texts ruin everything emotional problemy so dont text it.
oh yeah and, the reason why you were awkward with that one friend is cuz your both not the conversation starter people, or you were too worried about it that you perceived him too as a threat, or you simply came there unprepared without anything to say. so try to get your outgoing conversational starter people with you cuz they tend to be really good friends and are easier to hang out with... even if they say stuff behind your back.