When I (21nb) come out my Bf (25m) will leave me

Me and my bf have been together for three years. I do love him but I have come to the conclusion im am transmasc. When we first started dating about a week in he found out I was considering being nb, he got mad i didnt tell him and i apologized and figured it was a trust thing. a couple years later I told him i like He/They pronouns but hes only ever used they/them with me. Recently I told him I wanted to change my name. He got upset and we fought about it but made up. although so far I havent heard him call me by my preferred name. I keep trying to push the fact I wasnt happy like this down buts its all coming to a head, we keep fighting and he keeps making "jokes" about how he doesnt like masc people and how he should "be able to see women on the side". the jokes are starting to hurt my feelings because I know what i want isnt what he wants. I know I need to tell him soon but i get so nervous. we live together so im not sure what that will mean for us but Ive realized i cant be happy staying the way I am.