my girlfriend and i have been dating for 5 months. she says im her one and only and that im all she needs and that im good enough.but i feel like im not. even though she says i am. why do i feel this?

It is quite normal to feel this way, if you think she looks really pretty and you don't like the way you look(though you might be good looking), or it can be because you think she is smart or better than you in all ways. First of all you should trust her that she loves you and she thinks you are the best for her, just like you feel about her. And you should also try and believe that you are as good as she is and you both deserve to be with each other equally. If this doesn't solve your problem, do let me know in detail what is bothering you.

Why do you feel like you’re not good enough for her? Could it be financial wise? A difference in personality? Different family culture? There are many possibilities that is the cause of how you’re feeling now and these are just some of my guesses. May I know how old are you? Are you a working adult? Or a teenager? firstly, you might want to take some time to think about what you think you’re lacking at. It could take few hours, days, weeks or even months. Secondly, do you think you have high expectations for yourself? Why do you think you’re not good enough? Did you abuse her? Did you harm her? If none of these happened (which I hope), then why can’t you have faith and trust in yourself? Both of you had just started dating. It’s the the ‘getting to know each other’ stage of a relationship. It’s normal to actually feel some doubts in an early stage of a relationship. Because you’re still finding ‘the one’ that is suitable for yourself. Take time to know yourself and know what you really want in a relationship. Once you’ve understand it (and it’ll take some time. So be patient! You still have a Long way to go in life!), you’ll definitely find your own answer. Because no one in this world can answer your own personal questions as everyone works differently and have different mindset and preferences. A quote for you: sometimes, you will not get answers instantly. Life and relationship questions are not like mathematics or science questions where you just use formulas and get your answer - it’s way more complicated and time consuming.