Talk to him. See what's going on in his head. If he don't reveal anything don't press him too hard about it. Just fall back and watch his actions. Remember what's done in the dark always come to light.
Don't play games. Pay more attention to him, not less. Try asking for some quality time together doing something you know he likes. Most importantly, if you have relationship concerns, talk to him about it.
Talk to him, plead for honesty and except it...
Whilst I did like the first reply of showing less interest, showing more interest would be more likely to work.
Let me begin by saying communication is so important. Share how you feel , but don't press the subject, if he cares he will let you know. Don't act distant and indifferent to him, this may push him further away. By the way, you are absolutely beautiful and I hope you guys rekindle your relationship. And if it doesn't work out, don't sweat it, he's not worth your time and move on, don't waste your beauty....
Do something fun and be affectionate. And after that take some space back. If he still likes you, atleast you will let him thinking about it. Then talk to him about ur feelings and that you want to change those.