Hello and thanks for taking the time to answer my question.I have been dating this girl for quite a while now and I really do love her,but I don't think she really loves me back.she says she loves me and sometimes she means it by the tone off her voice.the only problem is there's this guy that is quite the good looking guy for what I have heard and a very nice guy.I am not the nicest guy around but I have come to terms with these.I want to be nicer looking for her and myself.she means everything to me but she is amazingly good looking and I feel like I'm holding her back from the guy of her dreams.I do not think that I deserve her in anyway and her happyness is the most important thing to me even if it means me getting hurt or while I try and show her I can be attractive but how I'm only a guy I can't do much.what can I do,or how can I help my mental state from being a mess.how can I keep her as my girlfriend she still really cares about me but I don't think that's anough?

Thank you very much for taking the time to help and I can't wait to look at your answers don't be afraid of hurting me id rather know the truth and keep in mind that I just can't get over and find another it would be too hard.

First off, don't compare yourself to others. If you want to be more attractive for you, to benefit her, then do something about it. Get a facial, get a mani/pedi, get a haircut, get some new duds. But if you think any of these things will make someone love you more or less, you're wrong. If she says she loves you what reason do you have to doubt her? You haven't mentioned one. You said there was this hot guy... are they friends? Cousins? Is she dating on the side? What? If they are friends, and it seems that nothing is going on, maybe nothing is. Has she given you reason to not trust her? How old are the two of you? How long have you been together?

Maybe your insecure feelings that you aren't good enough are making her think that you are the one that is not happy with her. Sometimes when people see that someone they care about is not happy about something they think it is them so your insecurity could be having a reverse effect.
Lighten up and be yourself. If 'n when she loses interest she will let you know. Don't push the issue or you could end up pushing her right into his arms.

Ditch the insecurities that will be a major improvement

Thank you for the answers but how do I put my in sercurites behind me

thank you for the answers but how do i put my in sercurites behind me

Do like Chi mama said and fix yourself up. When you are with her don't come off as negative, whinny, not good enough,. learn to have some self confidence and go for having a good time and relax.

See the problem is I just can't get it out of my head I have anxiety problems so that doesn't help she doesn't know but I get panic attacks all the time.so when I try to suppress the worrys it just gets worse and my head thinks every bad thing that can go wrong. I would honestly do anything to keep her

You need to learn how to over come the panic attacks.
Take sublingual vitamin B12.

Some other things you can try (from the natural health stores)
GABA, 5 HTP, Kava Kava, DHEA,

See which one works best for you but do not take with meds.

Avoid artificial sweeteners, such as, Nutrasweet, Splenda, and sugar and
Caffeine

Scents lavender or sandalwood essential oil works as one of the natural panic attack cures for calming down

see the problem is i just can't get it out of my head i have anxiety problems so that doesnt help she doesnt know but i get panic attacks all the time.so when i try to surpress the worrys it just gets worse and my head thinks every bad thing that can go wrong. i would honestly do anything to keep her
The best way to keep a girl is to talk to her. Tell her your worries, cause like mentioned before maybe she thinks the reason that you're stressing is because of something she did. Girls can tell when something is wrong, even if we don't say it all the time. Talk to her.

I know this sounds like I asking so many questions and I apologize but how do I stop thinking of the worst

It sounds like you have some self-esteem issues to work on. You may be "only a guy" but guess what? This "guy of her dreams" is "only a guy" too, as is every other man in this world. One of the worst things you can do is to compare yourself negatively to others. "Good-looking" is in the eye of the beholder. You may think this guy is "good looking" and maybe she does too, but rest assured, some other women out there think he's a dog. And I'm sure that lots of women in this world would find you to be a good-looking man and yes, some others would think you a dog as well. Same goes for me, for that matter and for everyone. I always felt that Demi Moore was a hot actress but I'm sure not every man in the world agrees with me. But, just because not every man in the world drools over her doesn't make her any less accomplished, any less rich or any less famous. And for those who are not prominently in the spotlight like that, the same still holds true. Not being the apple of everyone's eye in the world doesn't make you any less of a person and any less deserving of the things you want. So stop beating yourself up. There's lots of fish in the ocean ; if one doesn't work out for you, there'll be another one along shortly.

Just think about this.

There are BILLIONS of guys in the world, but she picked YOU!
There are BILLIONS of girls in the world, but you picker HER!

Quit worrying about everyone else. You are with her. Do what makes you happy, do what makes her happy. Encourage to make herself and you happy. When you are with her, everyone else in the world doesn't matter. Enjoy your time together. :)

If you give up on the fun, the "spark", and only worry about yourself, then your relationship will be ruined.