How do you get over jelousy?
I have been in a poly relationship for over a year now and so far things have been doing well, except over the past few months I have started to feel jealous towards my best friend Sam (who is also his wife), being with him more especially when they are having sex. I don't understand exactly why though since he shows that he loves me and says that he does, and even shows me, and most of the time I believe it, its just that when he and sam have sex I feel not only like crying but also punching her in the face. I don't understand though, he loves for me to be involved in the sex even when he is having sex with her, he also spends more time with me then her because of her job, and he always gives us both equal affection yet I always feel scared at times that I will land up being pushed away and forgotten.
I want this to be resolved especially before 6 months since his new girlfriend is going to move in soon, and I don't want to show anymore jealousy. He tried to help me by talking about it and sam tried to help as well, but I still feel angry and hurt when they get intimate and then feel even worse when he tries to talk to me about it. It's like I don't want to believe that I am jealous.
Please help me to resolve this, I love them both so much and I want to make sure that things will get better.