Jealousy Issues

My ex boyfriend used to cheat on me, repeatedly. That experience has left me distrustful and therefore jealous. Its been two years since I broke up with him and now Im in a new relationship for 9 months. The problem is that the more serious it gets, the more jealous I become. Im afraid he will cheat on me either sexually or emotionally. Deep down I know hes a good man and that he loves me but sometimes I am very jealous and it becomes unhealthy. Ive been checking his phone and messages etc... I feel angry when he even looks at somebody else. It is emotionally draining sometimes to me and to him. And weve had multiple fights about this. Im afraid itll only get worse. I am self-conscious and I dont know how to get over that whole jealousy problem. Its like theres this little voice in the back of my head telling me that everybody wants to do me wrong. How do I get over it?