1) I've gotten mixed up with all this work.
2) My partner mixed up what they were saying.
3) I get mixed up if I speak too quickly.
4) Oh, sorry, I got it mixed up.
5) I've gotten mixed up with all these issues.
I think maybe the first and last sentences seem a little off, but the ones in the middle ( 2,3, and 4) make the most sense to me. Hope that helps!