This is how cold hearted guys can be changed

What to Do When Your Boyfriend Is Cold and Distant
Give him all the space he needs: If he's fearful of loss of freedom or independence, he'll snap right back to normal with time. Cramping his style will only make him withdraw further, and that’s the last thing you want to do.

Love the hell out of your man: He needs you now more than ever before. Make sure to abide by the point listed above and love him while giving him his space.

Stay happy: In other words, don't worry or play games to try to get him to talk. Act like everything is normal, and don't let on that you're concerned about his behavior.
Reassure him that you trust and believe in him: Give him confidence by letting him know he can handle it.

Stay breezy/chilled out/calm when you're together: If he retires to another room, keep things happy and smiley. After a while, he'll come out to feel the love. Positive energy is like a yawn—contagious!

Set up some quiet time between the two of you: Remove all distractions, so that he feels like he can talk—and he just might! Be casual, though, and don't let him think that the sole purpose of this exercise is to make him talk. 

Reassure him that you're there for him, but also help him to understand why his behavior is upsetting you. Remind him through I statements that you feel left out when you don't know what's going on in his head.