Your while condition is faulty.
If answer[0] == 'Y', then answer[0] != 'y' will be true.
If answer[0] == 'y', then answer[0] != 'Y' will be true.
What you want is:
while (answer[0] == 'y' || answer[0] == 'Y')
PLEASE USE CODE TAGS (the <> formatting button) when posting code.
It makes it easier to read your code and also easier to respond to your post. http://www.cplusplus.com/articles/jEywvCM9/
Hint: You can edit your post, highlight your code and press the <> formatting button.