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It seems that your muscles are weak.Give some rest to you body from dancing and athletics for some weeks to subside the pain. You can do some hot water fomentation for more comfort. During periods body remains exhausted and due to that weakness of muscles pain gets more worse. So its advisable to not take excess strain during menstrual cycle.
When there will be a marked decrease in pain you can start your exercise to strengthen back muscle, prescribed by qualified doctor of Physiotherapy
. If pain wouldn't subside then you have to come for complete and detailed checkup.
I wish for your speedy recovery!