I don't think changing your post titles would have any effect on FeedBurner. How many subscribers did you have before?
Oh ok I read somewhere a lot of people have the lower feedcount problem due to various reasons. Figured changing posts that users subscribe to was one of them. I had 6.
Your "reader" count fluctuates from day to day. It depends on how many readers have requested your feed. If no readers request it on a given day, then it will be 0.