HELP!!!!!???? ANXIETY?

I'm afraid that i will get sick. I don't have a germ phobia. I just feel like the world is going to end if I get sick,I know it's not but, I feel like it is. I went to Wyoming over the summer and, well my dad said i just got altitude sickness. We went to this one restaurant and i felt sick so i stood outside while my dad finished. I could not get back in the car, I was really afraid I was going to throw up. After that we went home early. Ever since then, I get this really weired feeling in my stomach when I'm not at home (I'm at the store or something). I hate that feeling. We got back in May this summer. It was a really expensive vacation. And I feel really bad about ruining it. My dad really needed this vacation and my step mom makes me feel really bad about. She says "Why did you do this to your dad? He really needed this vacation!" Then she called me a "12 year old night-mare". And I would just sit there and cry and cry. Every now and then, she always says "we don't have any more money because we spent most of it on that vacation, that you (me) ruined." Please tell me what to do?! Btw I'm 12. And I haven't talked abut this with anybody except my mom and she doesn't know what to tell me.