Asking out for date to co-worker

Hi I am 25M working in a bank as 3rd party (vendor/resource) IT domain and a cute girl sits right infront of me 27F as she is also from different 3rd party but we are working in one team. We both know each other and we travel to the station together but her contract is going to end on March and I am afraid bcoz never asked a girl out ever and I am kind of afraid that our friendship will be ruined so please tell what to do Note - The 2 reason I am not asking her out till now afraid of rejection I have been rejected by many girls and boys because I am fat like 145 kg Please drop some suggestions.