I'm new to the MH board, so hello 
I've always been bit of a worrier, it's certainly in my nature. I was not a particularly adventurous child (but not a recluse by any means either).
As an adult, I've come to realise that I react very badly to stressful situations.
Overall, I plod through life doing quite alright. I have a wonderful, loving and supportive DH and 3 lovely most of the time DC 
However, when certain situations arise, I react in a very extreme case. Here are some examples:
If DH has a prolonged headache, on and off for days or maybe a week, I slowly get convinced he has a brain tumor.
He recently had ongoing pain in his groin area. After several trips to the GP, I ended up getting convinced he had pancreatic cancer.
I noticed one of my lymph nodes was swollen by my ear. After 2 days, I was convinced I had lymph node cancer. (Turned out to be a cold).
I'm the same with the DC.
It's not an immediate reaction though. If I have a headache, I accept it's just a headache. If I have abdominal pain, I accept it's period pain and so forth.
It usually festers into an extreme worst case senareo after a week or two.
I'm in the middle of a very bad episode at the moment and I'm really struggling with it.
I always manage to function OK and sort of pull myself through it. I go to work, see to the DC. It does not flaw me, but it's so hard at times.
After a certain amount of time, and often with minimal symptoms, I end up thinking really in depth about the worst possible outcome. E.g. with DH's groin pain, I ended up reading about cancer treatment, the success rates, different options, I have visions of being a widow, at times going as far as 'seeing' DH's funeral in my head. It can get very distressing.
These episodes are usually short lived and with DH's support, I get through it.
When things are positive, I'm fine. Happy and I enjoy life very much. When there's a blip in the road, I seem to mentally turn into a bloody mountain.
Does anyone else do this or is like this?