I have a new boyfriend but want my ex back

Help! I broke up with my ex in November and started a new relationship soon after that. I didnt realize how much I missed him until 2 months ago. We havent talked since the break up (almost 4 months), but about 2 months ago I called him a million times, he just hung up the phone and has never searched me. This situation is obviously affecting my current relationship. Should I break up with my present boyfriend to try to get my ex back? Or should I just force myself to move on and focus where I am at?