Someone wrote to Dan Savage about this a while ago. As I remember, she's an egalitarian in general, but sometimes wants to be a sweet homemaker whose boyfriend comes home, inspects things, and then punishes her for infractions by spanking her until she cries. She was very conflicted about this. DS suggested that she be egalitarian all she wants, and then when she's Suzy Homemaker she put on a special bracelet or necklace (we'd probably call it a collar) to indicate to him that she's in a different role. This is what I imagined from the OP. I also imagined that she was "pet" in the sense of being sub at that time, and not that they necessarily engage in pet play.

If this is right, and you generally have a vanilla relationship in which you indicate a desire for a temporary power exchange by engaging in some ritual, then I'd say, ditch the punishment. First of all, if this happened three weeks ago and he hasn't punished you yet, then move on. If you've reopened this post because something similar has happened again, though, then I would really say that you seem to be conflicted about this play. You're the one who chooses when it's going to happen, you appear to want it, so why are you undermining the power exchange that you've signed on for? It's more important to figure this out than to punish you for transgressions. (And the transgressions are so extreme, btw, for someone who's willingly in a power exchange that I would say that's an indication right there that something is wrong with the dynamic.)

Possibly issues: You want the power exchange but when it happens it scares you. You feel guilty for wanting the power exchange so you undermine it when it happens. The power exchange is OK but you feel bad that it's voluntary and wish that he'd "force" it on you. You don't want the power exchange. I'm sure that the viewing audience could chime in with a million other possibilities. Oh, here's another one. He doesn't want the power exchange, or something about it makes him uncomfortable, so the dynamic isn't working. See how fun and easy this guessing game is?

Only you and he can move past the guessing. I suggest that you really talk this over and figure out what you want out of the power exchange, and what you're getting and not getting out of it. This behavior isn't "bad", it's communicative, and you need to move beyond it.