i got my period two days ago, and with it, a very annoying, centralized pain in the right side of my back, towards the spine, about level with the bottom of my ribcage. it feels muscular perhaps, and it really only hurst when i move ,and is very sore, like the rest of my back. i also carry a one shoulder heavy bag a lot on that side, so i think that might be related. do you think that pms and the bag could be causing this pain and not something more serious? im a very young woman with no other health problems other than very severe pms. also my lymph nodes in my armpits are swelling, but i think that's due to pms.