USA social security payment as a company employee and sole proprietorship

Hello Japan Financiers,

I would like to verify some information about my current situation (which is a bit complicated) involving USA social security payments. Currently I am employed by a company in Japan but also have some sole proprietorship income. Last year was the first year that I have been employed by my company and so I am wondering how that reflects on my USA social security.

Up until last year with my sole proprietorship income, I paid my own pension here in Japan and could opt out of paying American social security by using form j/usa6. But now that my company pays my Japanese pension (and I don't pay social security / pension for my sole proprietorship income) will I have to pay social security on my sol proprietorship income in the United States?
Or is there anyway I can opt out of paying social security on that income like I did up to now?

Thanks very much for any insight.