A few thoughts for you ...
1. sleep paralysis and terrifying nightmares (these symptoms largely stopped when I stopped sleeping flat on my back or stomach)
.. sounds like some kind of situation that disturbs your sleep. Sleep apnea is worse for a lot of people when we sleep on our backs than when sleeping on our side.
.. my sleep tech told me that there is a theory that sleep apnea can cause nightmares. The reasoning is that the physical effects of sleep apnea and the body's response is similar to how the body would respond to situations that deprive it of breath and oxygen while awake. When it happens while asleep, the brain fills in the blanks with dreams about things that cause breathless panicked breathing.
2. I've always slept with earplugs in because if I don't, I wake up a lot/sleep really lightly. Then I wondered, if perhaps I still do wake up, I'm just not as aware of it because I can't hear anything?
.. people who have sleep apnea sometimes wake up from the SA and attribute it to other things. Nocturia (getting up to pee at night) is one of those, where people think that nocturia is waking them up, but once on CPAP therapy and sleep through the night the nocturia goes away.
3. I've been a low energy person as far back as I can think, at least since puberty. I have no frame of reference for a "refreshing" night sleep, I've always assumed all adults wake up somewhat "tired" in the morning and this is a normal part of aging (I'm in my 20s).
.. we just look that way to you young whippersnappers.
. It might be interesting to do some googling about sleep apnea onset at puberty. Maybe in cases where a person is not configured similarly to the average SA sufferer, there is a tendency for it to begin at puberty.
4. The idea of a solution bringing energy and drive seems WAY too good to be true. I don't want to get my hopes up, as I feel like maybe expectations of being refreshed, energized, etc., are unrealistic. But I am tired of feeling like my youth is wasted on anxiety, low mood, and exhaustion.
.. like others have cautioned, you gotta determine if this is the malady before you invest much hope in the therapy. I will tell you from my experience that CPAP therapy is the most life changing medical change I have made in the past ten years. I feel like I got my life back. At first I didn't wake up feeling totally refreshed, but I didn't feel like I needed a nap every day and that was a major indicator of good things to come. Within a short time I was feeling relatively great. I don't get the night's sleep I desire every night, but I am awake, alert, and feeling a lot better. I was telling my dad recently that for the first time in probably decades I could say I feel better today than I did last year on this day. That is huge and I attribute it to CPAP therapy. So IF you are diagnosed with SA then you can expect good things from the therapy.
5. It's emotionally draining trying to understand how to get a diagnosis and what the implications of the diagnosis, as well as treatment, are (sleeping with a CPAP machine??? this sounds so uncomfortable and weird)....... expensive... time consuming... intimidating.......???
.. it take a minor bit of getting used to, but once you find your sweet spot for machine settings and most comfortable mask (big factor for most people) then it is not uncomfortable nor inconvenient. For months I would imagine I was drawing sweet refreshing, healing oxygen through a magic straw, because that is precisely how it felt to me. Not a problem. Weird... a little, but so is being tired all the time. It's a good trade my new weird for my old weird.
6. I really know nothing, I've only just delved into this whole concept. Can anyone offer advice? Encouragement? Is it difficult to get diagnosed? Are there certain kinds of doctors? Expensive? Is treatment accessible? Thanks community.
Ditto to others who have said get diagnosed, you might find a different sleep disorder.
If you do find you have SA please return and post about it for others in your situation to follow your breadcrumbs. If you determine it is something else and you feel generous, please come back and post about it so others in your situation can learn from your experience.
good luck pixelkitty. Be encouraged that it is not normal to always be tired at your age and continue to pursue whatever direction your search takes you.
You have turned a corner now that you realize this is not normal and you are chasing it down.
You deserve to feel better and I sincerely hope you do and sooner than later.