Dude...first rule on staying loose is: stay loose. Really, though, it's not that hard...you are more than likely, as you said, 'over analyzing' stuff and therefore not performing to your liking...

...I've used one, I guess not so common, technique which I am pretty sure I remember reading that my favorite pianist used which was playing at full volume while you could barely hear...that is, with a vacuum cleaner on...a blender at the same time, perhaps...some Beatles playing...maybe a little Metallica...and there you are,...with nothing but the notes in your mind to guide you...and sometimes, when you come back...you end up playing it just fine...

...that, and throw yourself every week for years on end in front of the hoi polloi and see what comes back...

 

...I've used one, I guess not so common, technique which I am pretty sure I remember reading that my favorite pianist used which was playing at full volume while you could barely hear...that is, with a vacuum cleaner on...a blender at the same time, perhaps...some Beatles playing...maybe a little Metallica...and there you are,...with nothing but the notes in your mind to guide you...and sometimes, when you come back...you end up playing it just fine...

Reminds me of the part in The King's Speech when the speech coach has the stuttering royal listen to music on headphones so he can't hear himself and then records him reading Shakespeare and he speaks just fine. It would probably be different with playing music, though.

 

Practice slow.

 

Another is I can't seem to be loose and play fast, what are some tips on staying loose?

Drink plenty of alcohol beforehand.

 

I do practice slow, I tense up far too much sometimes when playing especially fast pieces. Especially when I am playing in front of people.

 

So you feel nervous in front of people? That's normal, just be confident and think to yourself "i am going to give these guys a blast" and start playing your piece.

What about when you are alone? where does that tension comes from? Have someone check that your shoulders are relax and not all tense up. Don't think of the individual notes in fast passage, play and think of them as a single passage.
Also in fast passage(actually in everything), your fingers shouldn't *press* the keys, but let your fingers drop and sink into the key using your arm weight.

 

I think it comes from fearing I'll mess up. I tend to over think in general.

 

The best playing is intuitive - ie from the subconscious. As soon as you think about it, you are bringing it to conscious awareness.
But you can only play accurately if you have practised and that practice has to be conscious.

 

And practiced slow. Slow practice is concious practice.

 

A couple of problems you have? A couple of problems pianists have!