you cant check for frame lables since _currentframe only represents the frame number of the current frame. Frame labels only help you manage your navigation with the use of gotoAndPlay/Stop.
However, as a workaround, you can do the following:
What this does is saves the actual _currentframe in the variable thisFrame, then goes to the label you want to check. Then it compares the new _currentframe with our old frame in thisFrame. If they are the same then the playhead didnt move and you are in fact on the frame with that label. The final gotoAndPlay returns you to the actual current frame as stored in thisFrame