a New Day, a New Disease!

I don't know what to do anymore! I am getting so frustrated and I know the people in my life are getting frustrated as well. I feel as though I haven't felt 'normal' or really good in like a year and half. There is always something that doesn't feel right with me. For a long time my chest was very tight and I thought I had cancer. I went through all the tests I could possibly get done with that and nothing was found. Then I started to get panic attacks, which of course during these moments I thought I was dying and I just felt so helpless. Then I started getting tingling and muscle spasms all over my body- I looked online and convinced myself that I had ms- I went and got the tests done for that and they came back negative. And I can't help it but everytime something is wrong with me it drives me crazy and I will convince myself without a doubt that it is this horrible disease. I just wonder if anyone else out there goes through this. I try so hard not to look things up online because I end up just freaking myself out more and getting ten times as anxious as I already am. So for a while now my left arm has really hurt. It hurts below the shoulder on what feels like the muscle. I will try to massage it or ice it to make it feel better but nothing really seems to help- (i have had ekgs last year to rule out heart problems) but somehow I still think it's my heart somehow- I also get palpatations not only in my arm but other parts of my body as well. Along with that sharp pains in random places- including my chest, legs, knee, you name it- they usually do not last long but it does get annoying. So my latest thing I looked up is that I think I have a disease where your arteries harden- don't remember the name off the top of my head- but now I think that is why my arm and leg have been hurting. I am only 21 years old and this is how my mind works- I don't want to be like this anymore- I see everyone else and they just seem so carefree! If I am like this at 21 I can't even imagine what I will be like when I get older. My mom says it's like I won't be happy until something serious is wrong with me- but I know that's not true because I just want to feel normal again!
So I guess I was wondering if anyone else out there drives themself crazy like I do going online and finding what could be wrong with them, and also if my symptoms could be part of anxiety (the random pains, palpatations, tight chest, and pain in left arm)
thanks for listening to my rant- my boyfriend and parents can only hear it so many times before I know I drive them crazy! Any help would be greatly appreciated!