if u have been lifting for some time now are you over training maybe? or if u have just started exercising it could be your muscles r not use to the movement yet and with time the muscles will adjust. do u stretch out when u r finished exercising?

i do an exercise ball tape when i get done lifting. i exercise at home. im also female, so our frames are different. the exercise ball stretches out the entire torso, arms and legs. if i dont stretch after i regret it. i had started back up with my wt lifting about 2 wks ago and my tibia moved out of place and stretched the acl. i wanted to avoid warming up and just get on with the lifting. i went back to warming up and the tibia now stays in place. it would pop out of place when i was in the shower and id have to push it back into place. painful.. now that ive gone back to correctly warming up and cooling down the problem has corrected itself.

you may need to see an othropedic, or sports medicine doctor. you may have done something to your diaphragm that is what its sounds like to me but im not a doctor.. its ok to take a wk or 2 off from exercising. ive taken a month off before. i now take 2 naproxen before i wt lift. it has a muscle relaxant in it.