I want to file an amended pleading and supplemental pleadings in a civil suit against me for (contested) debt, Pro Se.

First, please confirm those need to be filed as separate motions? Second, to which would a counterclaim resulting from new knowledge derived from Plaintiff's disclosure, discovery and response to my Motion to Dismiss and Sworn Denial (filed after Answer where Answer claimed insufficient knowledge) apply? In my Answer, I left it to 'Defendant reserves the right...' Also, would the amended pleadings be 'as a matter of course', 'to conform to evidence', 'relation back' or all of the above? What's more, I was improperly served, but this was only vaguely addressed in my Answer yet expounded upon via my disclosure, filed with my Sworn Denial and Motion to Dismiss (based on an invalid claim), where Plaintiff responded that the claim was outside of my original pleadings. Also, no trial is set yet.