I definitely know what you’re talking about because I was also taking Mirtazapine two years ago, I had no idea what I was in for, my dose was the same as yours and I researched this drug before taking it which is something I generally do and it had very good reviews on how well it worked. I did not sleep well and when I did, all I had were nightmares, I woke soaking wet and tired, I then learned what restless legs were all about. I tried to stay on them hoping that the side effects would go away but they didn’t, the feeling of having a hangover was profound and it took quite a while for it to pass, worst of all my doctor was not available for a couple of months so I tried to get help from other sources, eventually I saw a doctor who told me to stop taking them because my dose was low and I would be alright. I’m still amazed by how many people have very good results with this drug but for me it was a proverbial nightmare, I don’t think that the heavy feeling of being hungover is good but perhaps it might go away, there’s far better medication available to help you sleep and they don’t have bad side effects.