Hello
i can fully understand your situation. When I was 17 my hands started jerking above my head and it scared me so much, I didn't tell anybody about it. I was scared it was something serious that I kept fooling myself into believing it was nothing to worry about and ignored it.
Eventually, I had a grand mal seizure in front of my mum and dad and I was taken to hospital. I was referred to a neurologist and given medication which controls my epilepsy.
It was such a relief when I had a grand mal seizure in front of my mum and dad and they found out what had been going on because I told them that my hands had been jerking above my head on and off for a while. They were upset that I hadn't told them and were upset that i'd been worrying on my own.
Could you tell your mum and dad what you have been experiencing or maybe tell a family friend / relative who you can trust and talk to. It always easier to talk to people about things that are bothering you when they aren't so close to you. This is probably because you aren't worried so much about their reaction - I know that I didn't tell my mum and dad for so long because my concern was that I didn't them worrying.
Once you've told a family friend / relative then maybe they will speak to your parents for you and explain to them that you're feeling really anxious because you don't know what's going on.
I understand that you are scarerd about seeing a doctor but you will have to go and see a doctor. If you don't, you will continue having these experiences and not know what they are and it's highly likely that something can be done to control them by taking medication so that you can lead a normal life.
Once your parents know, you will feel better having their support. Let them know how anxious you are ask them to go to the doctors with you and take them into the appointment with you. I always took my mum or dad with me.
Good luck and take care