I concur with pretty much all that has been said here. Tight pre-flop play is not your problem, neither is being too much of a nit post flop.

Hand 1 is just ridiculously coolered with runner runner for a board straight where any K makes you a loser. Bad luck here, my friend.

Hand 2 is standard.

Hand 3, I don't get the jam. There are cheaper ways to lose when you're beat by the flopped 2pair or set.

Hand 4 confuses me. Unless the villan is raising PF like 40% or something, QTs is too weak to call the raiser here from the button. So you call and end up in a real pickle where you hit top pair and have absolutely no idea where you are in the hand. Overall, I don't like this one at all.

And if you're lost, try a subscription to GrinderSchool. I just got the 3 month one a while ago, just thinking 'What the hell, I'll give it a try." I can say that is has been a tremendous help watching the vids as the instructors are explaining their actions in relation to position and opponents. Worth the $$, IMO.