Let me preface this by saying it sounds like you're carrying around a lot of low self-esteem, which could be the major contributor to the insecurity and jealousy issues. You are obviously not content with yourself and I applaud you for realizing the problem doesn't lie with your gf, but from within. You need to take steps to accepting the things about yourself you cannot change and/or making improvements on the things about yourself you can change. When you say that she has to put up with you, I'm guessing the jealousy/insecurity issues have been interfering in the relationship. A little bit of jealousy is natural and healthy, at least in my view, but it's important to not let it control you.

As shezbut suggested, if you feel there's a problem with your physical appearance (not that I'm saying there is, as I've never seen you nor could I be one to judge-what's important is how YOU feel), then do something about it. Get some exercise, change your diet to accomodate more healthy, lower-calorie foods. You know the drill. Maybe get a haircut or buy some new clothes if you have the funds to spare. It's important to do it for yourself, though. This cannot be stressed enough. Doing it for yourself will be more empowering and it will build up your confidence. Speaking as a woman, I will definitely tell you that self-confidence is irresistable in a man.

When you say she gets on well with these other guys, do you mean they're flirting or just having normal friendly conversation? The distinction is important to make. Does it make you uncomfortable simply seeing her talk to other men? Or are you constantly caught up in a cycle of comparing yourself to them, finding yourself inadequate, and thus being unable to have a conversation with her because of the doubt and worry? If she's overtly flirting with them, then you may need to have a discussion with her about acceptable boundaries within your relationship. If she's just talking with them, you need to STOP comparing yourself to them. I know it's hard to do that, but just keep telling yourself that she's YOUR girlfriend, she chose to date you over all of those men so you must have some quality they don't have. Just be yourself. Not to sound harsh, but it sounds like with your present state of mind that you are setting yourself up to fail in comparisons as it is, so why bother making them atm?

Refer to my above statements about cutting down the comparisons. Remember, she is with YOU, not with THEM. Now, again, I'm not certain if she's flirting with them or just having harmless, platonic conversation, but I'll go with the latter after reading your opening statements about her. You may find that when you start making individual steps to build your self-confidence that it will be much easier to talk to her without constantly comparing yourself to the other guys she talks to. Having a lot in common does not immediately equate to being prime relationship material. Stop worrying about them or even her and focus on yourself.

Try making a list of your good traits. I can go ahead and tell you a few. You seem like a very nice guy, you are taking responsibility for your thoughts and actions which shows you have integrity, you seem to be very caring and thoughtful towards your girlfriend otherwise you probably wouldn't be here. And you are strong enough to admit your flaws and you genuinely seem to want to rectify them. That's incredibly admirable. A lot of people who suffer from issues of jealousy and insecurity often project the blame onto their partners and you're not doing that, which is great. So don't be so hard on yourself, Josh

Is this your first relationship? If so, how far in are you? I can tell you that you can't have all the goods in a relationship without some bads. It's natural to feel insecure and unsure at times. Even those of us who have clocked in a couple of years or more will feel that way from time to time. Especially if you're young and inexperienced.

Hang in there and best of luck to you!