Your man in the past used to be so caring about you, his unwavering attention and constant love made you feel very happy that you always wanted to stay with him for the rest of your life.
Over a sudden, things start falling apart and the good feelings you had become history. He changes completely and never cares about you anymore. You start feeling like he's taking you for granted.
Don't lose hope that early rather try these to fix your relationship:
1) Limit contact
Try out reducing the contact between you and him. Reduce the frequency in which you answer his calls, replying back to his messages. You can even stop sending him too many messages. Turn down night dates and attribute it to your fixed schedules. Let his loneliness make him wonder what's wrong. If he truly loves you he will follow you up.
2) Re-evaluate your relationship
Take time to honestly study your relationship. Evaluate for how long has he been taking you for granted. In the course of the study, you may unearth other flaws of his personality apart from taking you for granted. After this, evaluate whether he can change or not.
3) Leave him
This should be the last step you should take in a relationship when you notice that your boyfriend has reduced love and the attention he used to give you. Moreover, you only do this after trying the other ways to save the relationship with no results. Since he doesn't care anymore about your feelings, take a move and seek happiness elsewhere.