Help - I want to come out as Bi but i'm dating a man

Hi, I'm a 21 and have been dating a man for four years. I've known I'm bi for two years and started questioning my sexuality before that.

My boyfriend knows and he's open to me coming out.

I want to come out because it feels like by hiding my sexuality I'm ashamed of it. My family is VERY Catholic and homophobic so that doesn't help.

I will be watching a movie with friends and go to say wow she's cute, or sometimes the opportunity for a joke comes around, or missing out on Pride, etc. are some of the reasons I want to come out.

I just don't know how, and I worry people will ask why even bother coming out.

Advice?