Hey there, just a quick background on me, I've had hppd for about 12 years now.
I completely get where your coming from and the best advice I can give is to remember that you are very new to this and in time you will get more comfortable with what is happening.
At first, with me, I would get this sense of rocking, like being on a boat, when I was trying to sleep. This was a very strange sensation and woukd freak the fuck out of me at first. I would and still do get a lot of what I would describe as visual distortions when I'm trying to sleep in a dark room, I'm sure you can relate, and if I'm honest for the first like 5 years I would sleep with a night light on to help with this.
Today I still get a lot of these feeling but I don't notice them so much because I'm used to them. So just remember you are in the transition period between how you once were and how you are now.
Time. Time is what you need, I think. The first 3 years where the most intense for me personally. I think because there was not a lot of help for hppd out there ( today I think there is more help with places like this, so use them)
Also I just want to say to not get caught up in the thinking of 'I'm going crazy'' it's so fucked up'. I say this because I thought like that for a long time and in the end it only held me back. Things will change, you will learn to live with hppd, and maybe if you go about it the right way you will gain a strength that most people will never have.
That's what I've got to say reach out if you need, your only alone in this if you want to be.
B