Is there a chance I will grow out my speech issues?

There are some words I can't say. Like register it comes out completely different. I have a fear of saying words I can't say. I even go great lengths of using a completely different way of saying it. Sometimes when I talk I mumble I try not to but I always do. (I don't drink at all). Lots of people ask me i've been drinking but I don't. It's so embarrasing. There was this situation I was in that actually made me want to cry, I was talking to the lady at my school and needed to pick up the register and I tried aslkking for it but i couldnt say it. It took ages and the lady had to get someone else to help understand what I wanted. I could actually feel myself go red and tears come to my eyes. When it was over I had to hide incase I cried. When I talk the words in the sentences come out really muddled up. Will I grow out of it?? Im15 ive had this problem since i was like 8.