Vomiting frequently/ went into shock/ Addison's disease?

Hi everyone,

It has taken me way too long to ask for advice on the net, but hopefully someone who has been experiencing the same issues can help me out somehow as it has been hell trying to go through it alone.

My dog is a Border Collie x Heading Dog and we live in New Zealand. She is 3yrs old (her bday is in 3 days!) and weighs 14.5kg. She has been vomiting a lot since she was a puppy, she would vomit up her food, bile, white foam, you name it, but mostly food so she was diagnosed with gastroenteritis every time. I had taken to several vets and all of them found nothing particularly wrong with her, they just said she was sensitive. I tried putting her on different diets and she would be fine for a few weeks/even 2-3months sometimes and then she would end up vomiting again. We had ruled out so many things, but cannot seem to find the issue.

I thought she was just sensitive until a couple of weeks ago, she threw up blood and yellow bile. I took her to the emergency clinic and they did blood tests/xrays on her and found nothing. She vomited a couple of times after that (but did not vomit blood) so they did another X-ray but only found gas. She was allowed to go home after another X-ray was done which showed no gas after she passed stool. She was diagnosed with just gastroenteritis (again).

She had to go to the vets again but this time was for an infected paw. She was on Prednisolone and Cephalexin (600mg) for 10 days, and when she was getting tapered off the prednisolone (after 3 days of giving it to her), she started to tremble. I took her to the vets again, he wasn't too concerned and told me to finish the prescribed dose and that we should wait and see as she is probably just sensitive. She continued to tremble a few times after the medication finished but showed no other symptoms so I though it was just a side effect/withdrawal.

Now, is when it gets confusing. After a week of finishing the medication from her infected paw, in the middle of the night, she threw up some of her food which looked half digested. That morning, she started to look for grass and ate it, threw up multiple times and then went into shock. I never want to experience anything like that ever again. Her gums were pale white and she was losing balance and collapsed. I immediately jumped in the car with her and drove frantically to the emergency clinic. She started getting better once she received IV fluids etc. and they ran some tests on her again and wanted her admitted overnight. She hadn't gotten into anything toxic, it was just another normal night and the all the tests showed she was fine. They didn't know what to tell me and told me to go see our regular vets for more advice.

The next day, I picked her up then took her to our regular vet. He didn't think it had anything to do with the medication given for her paw and suspected Addison's disease (He thought the steroids given to her could have stopped her from vomiting during the time she was on it for the infection) and wanted to do a urine test and another blood test. Her urine test came back with a possibility of Addison's but her cortisol levels were fine from the blood test which confused the vet. He is now referring us to see a Vet specialist but we have just gone into lockdown (delta variant hit NZ) and now I don't know how fast we would be able to see them. I've searched up Addison's but the only symptom she is experiencing from the list is vomiting frequently/and going into shock. Not lethargic, no increase in appetite or thirst, and she wants to play all the time!

I am constantly worried sick and having to reassure myself that she is just sleeping when she is still. I can't concentrate on anything and I really hope someone would be able to give me an idea of what the hell is going on with my baby... Sorry if none of this makes sense as I am in so much stress, I feel like I just spewed out all the words on here. My dog is my life and I've always just wanted to make her happy, just thinking about something bad happening to her breaks my heart and makes me cry. Thank you for reading this long story and I really hope I can get some advice.