Double advantage....is there any rule against it?

Quote from Galadrian_DarkHeart >>

I am hoping someome can respond cus i can't see any info on it.

 If you have disadvantage by default for whatever reason. Then use reckless attack to get to a neutral roll. Does that mean that things like sentinel disadvantage bring it down to a disadvantage? Or are you then technically immune to disadvantage and advantage sources, cus you can't get more instances of either than the ones you already had?!

It is imperetive i know before bringing up a new char concept to my DM!

Yes, if you have a source of Disadvantage and a source of Advantage then it will make no difference if you gain more sources of either. The rules will have you role neutrally. 

Quote from Galadrian_DarkHeart >>

It is imperetive i know before bringing up a new char concept to my DM!

This is what the rules say about having multiple Advantage/Disadvantage.

If circumstances cause a roll to have both Advantage and Disadvantage, the roll has neither of them, and you roll one d20. This is true even if multiple circumstances impose Disadvantage and only one grants Advantage or vice versa. In such a situation, you have neither Advantage nor Disadvantage.