why do i get so much anxiety when i work out at the gym?

[Knifeboy]

normally im pretty confident but after my first set in the gym my blood starts to flow and i feel a high, like stoned but just mildly and i cant act "normal" i will worry and be self conscious so ill just look down or feel like leaving early. does anyone have experience with this? i can usually keep my social anxiety in check except for when i do this. =x if i go to the restroom and let my blood flow go back to normal im fine again but i cant keep going inbetween sets or i would look stupid