Obstructive sleep apnea diagnosis

Ok so this whole time I thought I had CFS because I had the symptoms and the GP put me on CFS diagnostic pathway. And now the NHS is saying I have mild obstructive sleep apnea (OSA). Symptoms include depression, fatigue, etc. Do I trust this diagnosis? Weight is a factor and I believe the NHS is fatphobic + I don't trust BMI measurements. Has anyone had this happen to them? I will start using a CPAP machine end of April and I don't want to get my hopes up but also...I do...because I would love to not be disabled. I would love to be less irritable, have better memory, and generally have more energy. But is mild OSA really why I've been feeling like absolute rubbish for several years? I don't know what to think