Boyfriend Troubles

Me and this guy started dating and things were going well until his ex text him and told him she think she might be pregnant. Turns out she wasn't and where i thought their conversation had no more meaning and therfore should stop she starts telling him that she misses him and all that jazz. So he came to me and i said the only way shes gonna get to u is thru me and at first she said no then finally she did what she had to do to and she agreed to the polygamy relationship. She then began to become jealous because she was always busy and i was always with him. He told me he needs a break and began to pursue a relationship with her then 3 days later break up with her and told me he just want to be best friends that still have sex because he doesnt wanna be in a relationship right now and that we should just chill and go with the flow. Ive talked to his mother and she says that i do mean a great deal because i am the 2nd person hes brought to his partents and that every other girl including the one that was in the polygamy was just in and out in the middle of the night. I have a lot of people saying that i mean a great deal to him but how do i get him to get me out of the friend zone and how do i get him to just want me and not others. I dont have a problem with casul 3somes but i want him to myself. And the females out of his phone.