Hey, it sounds like you’re having a really hard time from the Japanese surprise at your linguistic ability. Also, can you please stop saying that teaching English isn’t a real job? I know that it can be low-paying, frustrating and - if you’re an ALT especially - it can feel as if you’re nothing more than a human CD player. But there are many people out there who make careers out of teaching English, and I’m sure they would appreciate you respecting their choice. If you’re getting paid for doing something, surely it is a “real job”?
I’m quite a believer in psychological causes of symptoms such as chest pain. I generally get them when I think about stressful events.
So, it seems to me that it’s your attitude that’s causing you to feel so stressed out. Why does it bother you so much when Japanese people want to practise English with you? Why do you feel so insulted when they remark at your ability to learn kanji? It can seem frustrating sometimes, we all know it. The worst one is “wow, you can use chopsticks!”... but do you think they’re trying to insult you on purpose? Could it not just be due to a lack of education about foreigners?
I’ve found that most Japanese people are ignorant about the rest of the world, but that’s not their own fault. It’s how their education system works. I have a few Japanese friends who have lived in other countries and had their minds opened, but the majority are still amazed to find foreigners who have learned their language. Firstly, I think it’s due in part to the hoards of foreigners who come over here with ZERO Japanese - I guess they get used to that. Also, have you never (back home) met an immigrant and remarked at how good their English is? I don’t think it’s fair to call anybody a moron just for showing surprise that somebody has actually made the effort to learn their language. Usually they are just trying to be friendly, are genuinely surprised and want to encourage you. Of course, you get the odd xenophobe, who feels as if you are violating their very thoughts by understanding their language. It is very sacred to them, as patriotic people, and to have an outsider come in is almost like having a spy trying to break their secret code….
The thing is, though, you have come to their country and you are speaking their language. You can’t expect everybody to automatically accept this, it isn’t the general mindset here. I’m guessing that your reaction is down to an insecurity of your own. How do you react when people ask if they can speak English with you? Have you tried just replying in Japanese, saying “sorry, I really need to practice Japanese, can you help me?” I’m sure you can find some Japanese friends who are willing to speak Japanese with you, although sometimes you might have to let them practice some English in return, too.
Where do you live? Is there a language exchange near you? I’m in Hamamatsu, Shizuoka, and we have a Japanese-English language exchange every week, where we can practice both.
So you’ve made the list of things causing you stress. Now, try adding WHY they stress you out. Next, write what you can do to change them. There’s no good in letting them bother you to this extent. Either change the way that you think about them (tell yourself “wow, I’m good at Japanese” when somebody compliments you on your skills, not “how patronising, they must think all foreigners are stupid”) or do something about them. I hope you find the solutions.
Also… try giving yourself some time to meditate every evening, or if that doesn’t work for you, something that relaxes you (music, painting, going for walks etc)... it’s important to have time to sit back and look at your life, rather than letting yourself be swept up by it all the time.
Hope you can work it out 
