Your girlfriend and you have been dating for almost three months now you haven't kissed you don't know the right time what should you do?

When you are alone, look into her eyes and say "I wonder what would happen if I kissed you." She will probably say something like "Why don't you try it and find out." If she says something like "That's not a good idea" or "This would be the last time you would see me", then you know where you stand.