I was walking and accidentally stepping in a pile of wet mud which caused me to loose my footing and my heel slid out from under me to the side. Luckily I was able to catch myself, so I did not fall, but I had to brace myself to rebalance and prevent a fall from occurring. The unexpected jolt of my heel sliding out from under me and my reflexive response to re-stabilize myself caused me to feel some vibrating/jerking movements and shaking in the back of my head from.

This happened 3 days ago now and I have had a horrible headache at the back of my head that is radiating to the front and sides ever since. I find it hard and depressing to believe I am so fragile that this would trigger a concussion but I have been feeling horrible in the days since it happened and was not feeling any headaches beforehand so I cannot deny the timing.

Could this have caused a subtle neck injury or something like that?

This is whiplash, not a concussion. Your anxiety is making it worse.

How do I know you are struggling with anxiety?

Easy, you have written such an elaborate description of the event. Your anxious brain has been playing this event over and over due to your anxiety.

Do you think this was enough to cause whiplash? There was barely movement, although I cannot recall exactly as it happened so fast. But I am not super anxious about the event, more shocked at how horrible I have been feeling. Such bad headaches constantly every day and dizziness + nausea in moments where the headache feels less intense.

Is a slip like this enough to cause whiplash injury?

Good news: Not a concussion.

Bad news: Not necessarily psychological in origin. Might be a fragile neck. Might be an easily triggered migraine.

Good news: If it's a migraine, very easily treated, but you need to see a dr who can figure it out. No idea about neck pain