My girlfriend is insecure

Hello im 17M i've been in a relationship for the past 6 months with a 18F

The first month it was only thought texts i felt deeply connected to her so we decided to meet

When i met her i fell inlove with her even more

But later she started to show signs for frustration

She said that she didn't expect me to be this handsome personally i find myself average i dont workout or do anything the only thing that stands about me is being around 6.3/6.4

I found her really pretty and i could worship the ground she walk on but she keeps saying Random things like

You sure u like me or that i can do better

And it makes me feel guilty and bad all i showed is love and care a always buy her gifts and everything

And i put so much effort but her saying this makes me feel like im not doing enough

Can y'all help me to find a solution for this?or it's just a problem in her if it is how can help her to overcome it