Uncodable, it is hard to see things from other people's perspective. I don't know that your girlfriend would have broken up with you (and done it so insensitively) if she did not think there was something you had said or done she did not like (enough to break up about) so I would look at whatever the other people are saying, and, even though you know you are an "okay" boyfriend, etc., look at the specific behavior and see if maybe it isn't true? It can be hard to admit that we have a problem of some sort or another but maybe just being open to could-be-true and investigating, kind of as if you were looking at a story/someone else, might help?

When your friends and loved ones make claims like "lousy boyfriend and no balls" ask them for details, let them know you are open to listening to what they are saying and see if they can get down to more specific thoughts as to where you might have behavior that you can work on. Going along with people by asking for details can disarm their anger and keep you from defending yourself too much; it's a good middle ground; you don't have to "agree" with them, but you can still ask them for their point of view.

The ex-girlfriend does sound a bit insensitive though :-) You might want to see if you can figure out how to work on better communication during fights so you don't feel as hurt or the other person doesn't feel frustrated (because you put up a wall of defense or none at all, aren't "there").