I have had 3 people all tell me I am holding my bass wrong. Each of these people had their own way of holding but now I can't seem to stop wondering if I am really am holding it wrong. ***! Is there a proper grip?

I don't think you're supposed to grip the neck(like guitar players do). You're probably supposed to place the thumb of your fretting hand behind the neck, roughly in the middle, below your middle finger.

That's what I thought but a friend said I will get carpal tunnel in no time that way.

That's what I thought but a friend said I will get carpal tunnel in no time that way.

I'd find twisting my wrist round so my thumb could fret the E more painful. I remember in Bass Player, it might have Duff McKegan, but I'm not sure, saying he did that with his thumb, but really didn't recommend it.

Also, when you're fretting, don't pinch the neck between your thumb and fretting finger (which a lot of people do). Think more of pulling your entire arm back.

I have had 3 people all tell me I am holding my bass wrong. Each of these people had their own way of holding but now I can't seem to stop wondering if I am really am holding it wrong. ***! Is there a proper grip?

The bass should be in the same place on your body while both standing and sitting. Adjust the strap while sitting down with your bass then stand up, the bass shouldnt move from that spot on your body.

As for your fretting hand. Your thumb should be gently placed on the back of the neck parallel to your middle finger, while your fingers are loosely curled and relaxed in a one finger per fret position.

Most people would agree that the "proper" fret hand technique is to have the thumb(un-broken joint if possible) on or slightly above the middle of the neck roughly behind your middle finger. Using this technique effectively requires holding the bass in the "proper" position also. This means wearing the bass high and having the neck angled up. It's also important to keep your elbow out away from your body.
I fully respect those "saggers" out there, looking good when playing in public is important to me also. My advise for the low wearing bassist is to do what is comfortable.