Hi swimmer:
i am very sorry about your step dad. That is always hard. Is he doing better now?
I would definitely say that you are suffering from anxiety. I suffer from the same thing now and have been for about 6 months. I didn't realize that I had anxiety until after numerous trips to the doctor and of course, finding out what anxiety is. I suffer, and it sounds like you do too, from what is called health anxiety, similar to hypochondria. Like yours, mine came on suddenly. One night after dinner, I was sitting with my husband ( I am a 20 year old female by the way) and I had a terrible heart palpitation. It just felt like my heart skipped a beat, or did something wierd. I got very scared. So I started to constantly worry about it. Pretty soon I got myself so worked up about it that I had panick attack one night. Anyways, I have thought since then that I have had something wrong with me, first it was my heart, and just recently I was so afraid of having a brain tumor, I was pretty much convinced that I did have one because I was getting terrible headaches every day and I never used to. I got all of this brain tumor information off of the internet and it really scared me just as with my heart. My point being try to keep yourself away from the internet sites about health stuff. There is a lot of information out there and it is a wonderful resource, but for people like you and me it just makes things worse.
Believe it or not, I had the exact same symptoms as you... Especially the heart palpitations and the muscles twitching and the tingling feelings. It is amazing what anxiety will do to you. I never imagined it would be so powerful. It has a huge array of symptoms. Just try to stop worrying. The longer you let it go on, the worse it is going to get. At your age, the chances of there being something wrong with you are very slim, especially if you have visited the doctor recently and he/she had a good look at you. I know it will be hard to forget... Just give it your best shot. If things don't start getting better, go to the doctor again and tell him that you think you have anxiety and describe your symptoms and they will guide you on the right path. Anxiety is common, just read in this forum.
I hope this helps... Please don't hesitate to ask if you have any more questions. I'd be glad to try and help. Have a good one. ;)