Hello Vania,
If you read my posts you will se that I have been through the exact same situation several times. But you have to tell yourself that you did not get a concussion, because you did not get one. If you got one you would wake because a concussion hurts and normal sleep movements are slow, except if you Fall to the floor. My daughter hit my jaw with her head while I was at sleep some weeks ago, and I woke from the impact although the pain was minor. And btw a single subconcussive impact is not a problem.
Now, I cant tell you why you get symptoms, but its part of the game. For me it usually takes 2-7 days to resolve.
You have my deepest sympathy because we are in the same boat ragarding this and I know how frustrating and anxietyprovoking it is, but I think tje best you can do is to relax and try to move on slowly and make sure you sleep Well and perhaps get some gentle neck care.
BTW, When I get worry I hit my head in sleep I can find small bumps and sore spots in my head, so I guess this is normal but we just dont normally motiver it.
If I sound harsh it is not intended, but my english is not that well, so I hope you now that I just want to help if I can