friend regretting coming out to friends, no longer wants to be out to the world, but everyone already knows he's bi

Hello everyone, I am wondering how I can help my semi-closeted friend who seems to have went a full 180 on whether or not to come out... however as you can see by the title it's a little bit weirdWe are entering out senior year of high school. I came out as gay at the beginning of my junior year. this friend was more of an acquaintance at the time, but we became much better friends as the year progressed and around new years he came out to me as bi, told me I helped inspire him a bit, and he wanted to come out to more people. He told his family and some of his closer friends.Around this time he starts a relationship with another openly gay guy from our school, most of their mutual friends know about the relationship but, not quite ready to come out to the school, my friend considers this a closet relationship.Throughout this time, he has stressed taking his time but did want to come out to everyone. He wanted to dance with his boyfriend at prom and have that kind of be the way which would have been so cute. However, his parents didn't like this idea (though they are fine with him having a bf, they wanted him to be more low key about it) and as you can imagine he was pretty upset, and while its resolved with his parents he didn't dance with his bfAnywho, it's been a few months and now he hates talking about coming out whenever I ask him his thoughts and just wants to get to college before considering it, when just a couple months ago he was ready to tell the world. He had a bad breakup with his bf that involved cheating and he has expressed regretting ever coming out especially because he's bi and could go through life without ever being too open about also liking guys. It seems he's tried to throw himself back in the closet and I keep telling him he shouldn't be sorry for that side of him, etc, but don't want to be too pushy because he's the one that needs to be ready.I would like some tips on what advice I can give. Our school is very accepting from my own experience and I hate seeing him feel ashamed.However, I'm not sure if he realizes but a ton of people know about his relationship and that he's bi. One of his closer friends told a ton of people, they told more people, and you know how high school can be. People know he's bi/had a relationship with a guy, and this ads another layer to the situation which I'm not sure how to handle.Should I be frank and tell him most people know anyway? I'm sure he'd be a bit freaked out but it seemed like he was on the verge of letting everyone know anyway, and I think he knows some people have talked, so it wouldn't be a complete blindside. I just want him to be comfortable with who he is. It just feels like his reasoning for not being open is because the first non-straight relationship he has had ended so poorly. I don't want him to feel ashamed of that side of himself, and he wasn't feeling this way a little while ago. He has already come out to the people that matter in his life and I want him to know the rest shouldn't matter.. . . . TL:DR- bisexual friend was in the process of coming out when slight issues with parents and cheating bf made him regret coming out and start to hate the non-straight side of himself again. Waiting till college to completely come out and tell everyone, but everyone already knows about his relationship with a guy/his sexuality.