Calling with Middle pairs a 3-Bet
First you must be very specific when counting a hand, describe in more detail the particular situation, what type of tournament, what speed (normal, turbo), stack sizes, exact positions, type of player all that in order to understand the unique situation you are going through and thus express an opinion as accurate as possible because in poker everything absolutely everything depends on the context.
You must keep in mind a basic game plan, you say that you come out with 66 from early position? You don't think that you come out very loose from that position.
You also talk about what a reg player pays you but you don't say if he is tight or loose, passive or aggressive or if you have seen him as he plays before confronting him.
What range of hands do you think he has and what range of hands do you think he puts you in?
And what does your strategy say preflop? What is your plan against an opponent who 3-bet your open raise or calls you? What is your reaction plan to the different actions?
With that sea of questions that I have asked you, what I intend is to let you know that for each particular action you face you must have an attack or defense pal already built (strategy) in order to react in the best possible way, you cannot leave your "Luck" the decisions to be made, you must have them elaborated, this is how you progress optimally in each phase of the game, in each situation.
You must have a Preflop strategy, a Postflop strategy, know how to play without position or with position and thus you will know how to react to each play, each street.
Start there, study
poker strategy, study put it into practice and little by little you will understand better the different situations that will arise in each street.
Before playing review your strategy and stick to it, if something fails, check it again and apply the necessary improvements, your game will improve and your understanding of it.
Cheers
