Experiencing the exact same symptoms as others here.
I've had trouble getting to sleep since I was a teenager (now 35) and around 25 started drinking to help get to sleep. Started with 2-3 a few times a week but the last few years have been 4-5 every night consistently along with melatonin 1-2mg when I was having extra trouble. Went through some pretty stressful life events around mid June of this year and since then I've been waking up middle of the night and feeling extreme anxiety during the daytime. The stressful situations resolved themselves but now I'm going through almost identical things as the OP. Around the same time in June I reduced the drinking back to 2 per night, started exercising 2-3 days per week (never have before, at all).
I used to sleep around 10:30-11:00 and wake up around 7:30 feeling great. In June it started by waking up around 5:00 and not able to fall back to sleep at all. I thought it was the sun (new house, big windows. no curtains), but fixed that to pure darkness. I thought it might be from GABA effects due to reducing the alcohol so I increased that back to 4-5 drinks per night, but I only think that made things worse. Then mid July it became waking up at 3:00 with heart pounding really bad, extremely hot feeling (but never sweaty), and cant get back to sleep for hours. Sometimes I would get another hour or so of sleep before getting up at 7:30 but othertimes no more sleep at all. Some nights I would even wake up at 1:00, sleep after 20 mins or so, then again at 3:00, stay up for hours, then sleep again around 6:00, alarm at 7:30.
I think the anxiety was certainly exasperated by both the drinking and the sleep deprivation... My GP prescribed Trazodone which taken about an hour before bed literally knocks me out. But when I wake up at 3:00 I still can't sleep, but get super dizzy instead.
Eventually I started figuring out that if I sleep another 2-3 hours after 6:00am I have deep rem sleep and vivid dreams, waking up around 9:00 feeling much better. That allows me to function in the daytime better since I'm not having the anxiety / emotional instability of sleep dep.
For medical stuff I first suspected hyper-thyoridism and checked T3 - T4 tests which were perfect. Then checked kidney liver etc all functioning fine. I checked hormones in general (testosterone, progesterone, estrogen etc) and my T levels were very low. Ref range was 200-1000 mine was 170. Started HRT with injections twice per week around mid July. Progesterone was also low and started supplementing that about 3 weeks ago. Neither of those has had a positive impact in sleep maintenance yet.
Three weeks ago I did a cortisol saliva test that came back perfectly normal. Elevated in the morning and tapering down to almost 0 at 10pm. I also gave them a vial of the 3am saliva but they "forgot" to test it... I might have to suck it up and order another one to see how high it is when I'm waking up, or if it's not high and means it's something other than cortisol.
Two weeks ago I finally went to a Psych and he prescribed Diazepam for 7 days tapering to get off the alcohol. Haven't had any at all since then. On day 3 and 4 of taking the diazepam I slept a solid 8 hours and felt great for the first time in months. Then I was tapering that down to 10mg per day and started waking up again (but easily falling back to sleep this time). Stopped the Diazepam 5 days ago, and had been feeling great, but for the last two nights in a row I'm right back to the 3:00am - 6:00am sleeplessness. I started a new (more stressful) job also 5 days ago, but it hasn't gotten stressful yet, I'm actually bored until the work actually hits. But I can't do the extra 3 hours of sleep between 6:00 to 9:00 anymore.
I've done lots of tests but not much attempts at supplementation. Given the alcohol background, are there any other suggestions that might make sense?