Mean what you say and say what you mean...
"I'm not looking to be in a relationship at the moment, I have this ice box where my heart used to be and I'm so cold, I'm so cold, I'm so damn cold"
"I know it's only been three days but I feel like I've known you all my life and I don't want to be with anyone else."
Your face at this time is probably just as screwed up as anyone who is told one thing one day and told another in less than a week after. The problem with people is that they say what they believe sounds good. Their mouths are used just because they have them, usually the words they give birth to either make no sense or absolutely do not apply to their lifestyle.
In other words :
"You not about that life, shorty"
A guy will tell you they don't care who you talk to, that they'll do them and "you do you", then text you saying "Why did you put a smiley face after the tweet you wrote to so and so, you know smiley faces mean that you're DTF"
A woman will tell you their last relationship ended terribly and they don't want to rush into things, and a couple days later pour their hearts out to you and express their "new found love".
If you tell someone you don't want to be in a relationship, you can't blame the individual for exploring other options, especially if that person is ready to settle down and was told that you weren't, from yourself.
Mixed signals might possibly be the number one reason why so many relationships never make it to their full potential. People are too worried about how they look, they care more about protecting their image than they do their unseen feelings.
The moral of the story :
Mean what you say, and say what you mean...