I believe there’s a great photo in everybody, no matter how un-photogenic they think they are.
The best headshot photographers have a natural ability to put you at ease and leave you with images that will have you saying “Yes, that’s the real me…”. Trust them – they’re professionals! Try practising your range of expressions in front of a mirror and get used to looking at yourself as others see you. They’re not looking at your perceived flaws, they’re looking at the whole wonderful package that is you.