I've been told that I have a nice tone on the clarinet but too spread out and not focused enough. I'm not sure what to do to make it more focused though. I think I breath correctly and have proper breath support (hopefully anyway lol). Can this be caused by incorrect embouchure (I don't think my embouchure is the best) or is this something I will develop over time? thanks

Smile!

No, seriously, smile. Feel you chin, and if it's flat, try to use the mucsles you use for smiling to hold that flat, and have you lower lip be just a thin, stretched layer between your teeth and the reed. Close up the corners, and don't worry about squeeks. If your having trouble producing a sound, close your corners more, and take in less or more mouthpiece (I forget.. experiment a little.)

If that doesn't help, I'd recomend private lessons. Oh, and test your embochure on an open G.

No, no the SMILE method isn't the way to describe it. When one smiles, the corners of the mouth become taut and spread apart, in a sense. An ideal embouchure has the chin flat, lips over bottom teeth, and corners of the mouth in, applying gentle pressure to the sides of the mouthpiece.
Be careful not to use too much pressure, because you'll get tired and air will leak out from your mouth.

See also http://clarinet-lessons.blogspot.com/2007/02/rebeccas-relatively-quick-guide-to.html

when i play alot my mouth gets tired and its REALLY REALLY hard to keep the air in

^the solution to that is to practice shorter amounts of time more frequently. for instance, if you're supposed to practice half an hour a day , but you get tired after 15, don't just fight it out playing ineffectively, take a break and come back fresh. you'll build endurance over time.

its at school and i have it for an hour