FWIW, my wife has to go to that "naughty place" in her mind to come. Watching videos of lesbians kissing helps her too. I think that for women, reaching a climax is 80% mental and 20% physical.
My first wife had much the same problem as you, and she was overweight too. She had a VERY small clit, that was hard to find, and was SUPER sensitive.No vibrators or rough handling...I found, that when I finally discovered it, that if I was 'very' gentle with my tongue, she could orgasm...but ONLY once. ...after that she was too tender to continue. For much of our married life, that was the only way she could orgasm..penetration did NOTHING for her...so I spent a LOT of time with my face between her legs..after a while she relaxed enough to let me lick her. Thank god I love eating pussy,and making my lady happy..
Take your time and explore in front of a mirror. Masturbate alot... it helps. Ask your gynecologist about how to separate the labia and show you all your parts down there. Most doctors and medical would show you and will use an abundance of caution to not make it awkward but rather a learning opportunity.
Tell him to explore with his tongue and fingers until he finds it. Repeat as necessary. If that doesn't work offer to grey someone to help him
No need to be embarrassed...don't be shy to ask, after all you are paying him/her for the service and consultation...in matters of sex in a room between 2 persons whether of the same sex or not, you can freely communicate with each other without embarrassment esp if it is a professional visit n consultation and check with a stranger not known closely to you and who you may never see again