I think you still might have a shot with your bf. But as anita said, you need to be very honest with yourself.
I think it’s important you don’t blame anyone else, but try to figure out how you contributed to this mess.

I’m wondering why you clung (?) to a person who was not a good enough boyfriend to stay with you, nor a good enough friend to actually stay in your life and be a real friend? You seem to have known that you weren’t “just friends”…
And how can you keep a relationship of 7 years from a “friend”??

I can understand that your bf has lost trust, even without your ex saying to him what he said. So you need to build that trust up again by being very honest about your mistakes, about what happened and about what you feel towards him. If your bf is not a total asshole he will give you the chance to tell your part of the story after he has worked through his initial anger.
You can’t know if being honest and open is enough to get back together and try again, but it is the first step, and necessary for clearing up this mess and forgiving/not fostering any more regrets.

(You could maybe let him know that you want him to know your part of the story which is very different from the version he has been told, but that you understand his anger/confusion and respect his space, so that he should let you know when he feels ok to talk about things…)

I wish you the very best!