Hey Gazza and welcome to the forum;
I admire your bravery for reaching out as you have; it takes guts to disclose very personal information to strangers and ask for help. So well done!
Traumatic experiences do affect the brain, so you've hit on something there. I'd call what you experienced - 'a trauma response'. Please don't feel bad as every person responds to situations individually.
When in danger, the primal brain is programmed to go into fight/flight/freeze mode but when we don't have closure at the time, it stays with us inside causing flashbacks, triggers and symptoms like anxiety and panic; PTSD or Post Traumatic Stress Disorder.
I understand this concept as I've gone through it many times. Having a psychologist to speak with is highly recommended as is keeping a daily journal to track your behaviour to identify common times and situations for self assessment.
CBT (Cognitive Behaviour Therapy) is most commonly used for trauma. It's also called talking therapy because that's basically what you do with your therapist. Face to face can be difficult for the first time, but please don't let this deter you from seeking therapeutic support.
Finding help as soon as possible is advised as the symptoms and behaviour you mention can turn into addictive patterns causing more problems than it's worth.
Learn to be mindful; in the moment focusing on your physical environment, not in your head. When you do this the brain registers there's no threat and decreases hormone activity like rises in adrenaline and cortisol. Taking long deep breaths while doing so will tell your brain you're safe as when we're scared our breathing accelerates. In essence, you trick the brain through conscious actions.
After you've calmed, write in your journal about the experience for future comparisons, event counts or to identify triggers as part of your self assessment routine. Take your journal with you to see your psych too. If you forget times/dates etc, it's handy for instant recall.
I hope this helps. If you have questions I'm here most days.
PS...everything will work itself out ok. :)