Most Helpful Guy
I think that you really DO need to end this relationship. I say this for three reasons. 1) It's not fair to your current boyfriend for you to still give part of your heart to your ex. 2) This new relationship is clearly not fulfilling you.
And 3), the most significant reason, is that it sounds like you have deep and serious issues that you have not yet overcome. If you want to have the happiest and most fulfilling relationship that you can, then you need some time on your own to heal. You need some time to learn more about yourself, to rediscover yourself.
You need to identify where all this pain and suffering is coming from. You need to be able to face in some way whatever it is that is the source of your torment.
But the one thing that you must do, difficult as it may be, is to leave your current relationship. Staying in a relationship that is unhappy, unhealthy, and unfulfilling will do nothing more than continue your cycle of suffering, especially if you continue to long for your previous boyfriend.
None of this will be easy or fast, but it must, and more importantly, CAN be done.