Ok let me clear a few things up, first of all, the people just arguing with the OP for the mistakes she did and even trying to get her in jail is ridiculous, we are here to help, not prosecute anyone.
And regarding the post, yes I do have to admit what you did was wrong BUT that doesn't mean you are screwed, you graduated 5 years ago and unless your ex-boyfriend has strong evidence to get Cambridge to investigate into this matter nothing is going to happen to you. Cambridge have much better things to do then to take a complaint from some angry dude, I doubt they will bother to investigate one of their graduates who was here 5 years ago.
And besides do they really want to spoil their prestigious name by sniffing out one of their graduates who cheated their way into their degree ages ago? Not worth it if you ask me.