I don't know what is going on, but i will try my best to explain my problem.
I am 20. When i smile or laugh( usually when i fake them, or the duration is too long, or combine of both) at some point i have to be forced to stop smiling or laughing cause my facial muscle gets "tired." I don't think tire is the right word but i can't find a better word within my knowledge. And it's definitely not pain. I can be consistent and run for 30 minutes even if i am very tired but i can't be consistent and continue smiling when "it" comes. I have to stop smiling. It's like doing too much bicep training with dumbbell and when you reach your limit you can't lift any more. I am 20, this problem is making my social life a total disaster.. please help, comment, advice, anything. If i am in the wrong forum, please tell me where to ask.