Trouble with my jaw and speech?

Okay about 4 years ago I was on a pogo stick (had to for gym) and I slipped off one side of it and smashed my jaw into it, the pogo stick was made from metal, and it hurt my jaw so bad I didn't go to the hospital but I couldn't open my jaw more then a centimeter for almost 5 or 6 months, and now I am 15 and I still can't fully open my jaw I can maybe open my mouth about the width of my index finger any ideas of what might have happened? And also I slur my words alot and people tell me I have a lisp or something but I dunno weither I do or not, and sometimes when I speak I have trouble concentrating on what I am saying or I forget or I start stuttering, and I also have been in a BMX accident or crash what ever you wanna call it and I hit my head off the pavement and my bike landed on my head could that have anything to do with anything? Can someone please explain whats up with what I just explained about how I speak please 10 points to best answer