#Do they need to know?
Do they need to know?
The first question you should ask yourself is, do the other players need to know that you play Dr. Jekyll/Mr. Hyde? If not, then you need to find a way to tell your GM what you do and when you do it.
##Leaving the others in the dark
Leaving the others in the dark
There is a quite simple way to get info past the others without them knowing, and that is writing a quick note passed over. You might use text messages/WhatsApp or something similar if you have relaxed table rules for such things. Best combine it with some sort of misdirection.
This method to inform the GM (or just other players) of some plot you are doing works best if everybody does this and uses it for even trivial stuff.
For example, the Paladin-Player hands a note "I want to help the poor woman A to find her husband" to his Cleric friend, they nod, making that a whispered exchange before they announce their actions to the group. The Rogue meanwhile might announce something (see the anecdote) and do something entirely different to build up plots and gears to work later.
A big caveat though: This method works better in groups that are ok with some intrigue and side-quests and is best answered by the GM to also use the method to distribute information. This increases the chance to play the character and helps with the distinction of Player/Character information.
###Anecdote
Anecdote
This is what I did once to keep the other players in the dark, more for the comical effect - and to prevent all a loot debate who would benefit most:
R[ogue]: hands a note "I will stick the healing Gem into the Paladins Pocket" to the GM "Finders Keepers, I don't tell the others and pocket it."
GM: nods "OK, can I see your sheet a moment? Hmmm... Roll against 12... Your Mod is +2"
R: clattering dice "13, got it."
GM: "You succeed"
[3 hours later, the paladin falls to the ground with 0 HP]
P[aladin]: "Ok, did my job. You finish the Dragon for me..."
R: "I don't think you are out of combat yet. That healing gem..."
P: "The one you stole and our PCs don't know about?"
R: points to the slip of paper "Yes, that one. It's in your pocket."
GM: nods