[cranks]

You should check with your mom if she got you your 戸籍(koseki). If you were born in Japan, and your mother is Japanese, you are technically a Japanese citizen in principle. If she's filed your birth certificate, your 戸籍 is still sleeping in an cabinet in some government building. Then you don't need to deal with the hassle of getting the citizenship. You can just go "home" and ask for your Japanese passport and/or file marriage with your husband.

If not, you probably need to go back to Japan with your mom first and get Japanese citizenship, which shouldn't be very hard and should not take years.

edit: I missed your post. Did your mom filed your birth certificate(出生届け)? if so, you probably have 戸籍. It is not online, you or your mom needs to send a mail to the goverment office where your 本籍(honseki) is.