It was in the 20's about a year ago. (Most of those points were from an answer I posted in stack exchange's Math group.) Now it's 1. The only thing I can think of is getting "This question already has an answer here:" once or twice. Is there a history of my rep changes/votes, etc?
It was in the 20's about a year ago.
You only appear to have been a member of this site (Pro Webmasters) for "3 months" according to your Webmasters profile, and all your (Webmasters) rep seems to have been gained from a single question asked just a few days ago.
(Most of those points were from an answer I posted in stack exchange's Math group.)
Note that the different Stack Exchange sites (Webmasters, Mathematics, etc.) all have separate rep scores.
However, you "only" appear to have been a member of the Mathematics stack site for 7 months, according to your Mathematics profile (during which time there doesn't appear to have been any activity at all?). If questions were closed then it's possible that they have since been deleted, so you may have lost rep that way? (Although "duplicates" aren't usually deleted in my experience, but maybe this depends on the site?)
You do, however, have a rep of 51 on StackOverflow and on SO you have indeed been a member for over a year - maybe it was this site you are remembering?!
Is there a history of my rep changes/votes, etc?
Within your profile page on the respective site you can see your reputation changes over time since you joined. Profile > Activity > Reputation. For example, on the Webmasters main site: https://webmasters.stackexchange.com/users/77870/jack-ritter?tab=reputation&sort=time