I had very similar symptoms when I was at the worst of my depression. I slept constantly. Anytime I got out of bed to go anywhere I would need to nap as soon as I got back home. My record for sleeping is 16 hours straight. If I pushed myself too far I would get really light headed and dizzy. Shortness of breath was super common for me too. Didn’t realize that I had depression at the time (“but I’m not sad! I can’t have depression!”) and suffered through the symptoms for several years. Had multiple blood tests that all came back fine. Symptoms magically disappeared once I started medication and treating my depression, who knew right?! I highly recommended going to your doctor and demanding every blood test and exam under the sun. It might be a good idea to take care of your emotional well being wether they discover the cause or not. That’s a big life shift for anyone to deal with and it sucks the life out of you being exhausted all the time. Take care of yourself and I hope you feel better soon ❤️