That's rough buddy. You know you can be fluent. Here is what I think might be happening. You really like this person so you want them to like you. Either they will or they won't don't put so much pressure on the outcome, if it doesn't work out it's not the end of world. You are thinking very hard about what you want to say. When you preplan your speech your subconscious goes uh oh we stutter on that word or phrase and then you stutter. Try not to say what you are thinking say something else entirely. Or think in general themes and just try to speak off the cuff. You are also probably pretty awesome and they might not think you stuttering is a big of deal as you think it is. Good luck and either way don't be to hard on yourself that is not going to help :)