I was awarded 30% service connected for sleep apnea when I left the military in 2008. In 2013, I was directed to and took another sleep study. It was found and the VA agreed that I needed to start using the CPAP. VA reviewed the evidence, agreed, paid for and I have been using the CPAP since 2013. In Sep 2019, during a review of my records, my representative informed me that using the CPAP meant that my SA rating should be 50% versus 30%. I filed an increase claim and was increased to 50% with an effective date of Sep 2019. Shouldn't the effective date be April 2013 when the diagnosis was received and approved? I checked and the 50% rating for using a CPAP was in place in 2013. I wasn't aware of the rating difference at that time, so I didn't file a claim at that time. I'm asking because I'm thinking I may be due some back pay...……….