OMG, meegs, I could have written your post myself!! I have SUCH weigh-down issues - I even had my stylist cut some shorter layers in it last time, which did help some. I also find that it looks better (on me) just below shoulder length as opposed to bra strap length.
It's such a fine line for me between enough moisture & being overconditioned. I have found the Rusk Calm Leave In/Detangler has been working very well for me, as long as I only spray it on the lower 1/2 or so of my hair. My hair is highlighted, so it needs some moisture, but if it gets anywhere near my roots, I'm doomed to having a flat hair day