I'm answering this because you mentioned the pain comes only in these exercises which definetly put load on neck & other mucles. As of now we can't tell the exact reason of your pain but one of the reasons could be tightness in the muscles. Try releasing these muscles in & around neck face upper back & chest with gentle massage which wouldn't worsen your condition as its safe prior starting your yoga sessions. Good luck!

Hello sinusitis Migraine Hypoglycemia should be ruled out consult physician for further evaluation and treatment.