Question about coming up with what you are going to say before you speak.

Question about coming up with what you are going to say before you speak. Lately I have been stuttering a tad more and got to wondering about how people think of what to say before they speak. I used to be able to talk without thinking of what I wanted to say but lately it seems that if I don't think of what to say before I speak I block till I come up with something to say. Does anybody else have this problem and if so how did they overcome it?