Verified answer

Your diaphragm is a plate muscle which assist the lungs to breathe, you can not sing from there. It is biologically impossible. If the plate muscle is hurting you are singing incorrectly.

Any good voice coach can teach you correct inhalation and expellation for singing.

Go get a voice coach and stop trying to teach yourself as you will do laryngeal damage and more than likely grow nodules. Don't be like Adele

It means your technique is incorrect. You need to find a classically trained singer and have some real singing lessons. Try to find an opera singer to teach you - they know all about diaphragms and voice control etc