Maybe. For Forgery charges, what is important is whether the document was made without authorization. It is very common in committed partnerships for one partner to give the other partner the authority to sign a document or check on behalf of the other. Because of that authorization, even though you are signing their name, the document was not falsely made.
However, if spouses each have individual bank accounts, and for those specific accounts they both know only they themselves have authority to write a check, the simple virtue of marriage would not allow one spouse to sign the other spouse’s name. This is also important during separation or during divorce proceedings. Signing any document, financial or otherwise, as your partner during such times can be criminal, and the simple fact that you were still legally married is not a defense.