What's wrong with me...?

well there is nothing really wrong with you.. I'm 25 and still have the same problems sometimes. It may be that your brain tends to think faster than you can talk and in reality it's supposed to but your thinking so fast but the words come out wrong because you can't keep up with what u want to say. Resulting in mixed up words or sometimes even stuttering...just take a deep breath and try to slow down that what helps me.