Yesterday I had 291 votes in total (261 up + 30 down, something like that). When I visited my Stack Overflow page today, I had only 253:
What the heck is going on here?
If my votes don't come back, I will kill myself.
Looks like, you upvoted the same person continuously more than 5 or 6 times, that probably hit vote fraud mechanisms, and probably all the votes to that person got cleared retroactively.
Probably questions/answers that got deleted - when this happens, all votes on them "disappear".
As far as I know, there is a weekly job that clean the place up and delete questions with negative votes that have no answer, maybe even with zero votes.
So as yesterday new week started, I guess that job kicked into action.
Now you say "but I upvoted" - good point, do you have habit of "pity voting" questions with -1 to bring them back to 0? If not I'm also at a loss here.