Ok, i am new at this, but whenever I bake large cakes ( 14" x 3" square or round ) the middle come out runny and I have to cut it out. What the heck am I doing wrong. It is sooooooo frustrating. HELP!!!!!!

You're simply not baking it long enough.

Others will tell you to use a heating core or a flower nail. I've been baking 50 years and have never used them.

Also, 3" is pretty thick for cake. It will take a LONG time to bake. I only bake 2" tall layers.

as leah said, you need to bake it until it's done. Here is a good referenc chart on APPROXIMATE length of time needed for baking. Since you're using 3" pans you'll need this chart. Notice that the larger pans are baked at a lower temperature since they bake longer, this prevents the outside of the cake from over baking while the middle bakes til done.
http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-3-inch-pans.cfm

if you use 2" pans you'll need this chart
http://www.wilton.com/cakes/making-cakes/baking-wedding-cake-2-inch-pans.cfm

Sounds like maybe your oven is too hot, if you are taking them out afraid they are burning only to find the middle is runny....