I felt compelled to post .
I am the same. But I am much older than you and never had an orgasm with my DH in all the years we've been together. I find it hard to write this, but I am seriously- at my age- considering leaving my marriage because of the poor sex. I don't want to live like this for ever. I feel a failure and feel my sex life is a failure.
DH is a sweet and lovely man. But the sex has never been 'whoooorgh'! Always just 'cosy'. Never ripping clothes off even from the start.
Before him, I'd had a few partners, but only one really knew what to do and I was self conscious and had never orgasmed on my own anyway then.
I didn't orgasm on my own till my 50s. Then I got a vibrator and it's easy. DH doesn't know I have a vibrator - I feel self conscious telling him and even though he's suggested 'we' get one, I can't own up.
Like you, when we are having sex I can't let go. Something about him inhibits me. He's quiet, he's kind, he's too eager to please in some ways but lacks imagination, He doesn't appear to like to finger me, He never does and even when I ask he doesn't. . He' s not that keen on giving oral either , even though I ask him to, and when he has it's not that great anyway.
Some time back I had a one-off fling with an old friend, who I fancied like mad, when things went too far. I used my vibrator and came. What it showed me was how I could behave differently with another man. Maybe it was easier because there was no history or expectations.
I think you need to accept that perhaps you and DH are not a good fit sexually. You could try seeing a sex therapist together or on your own. You could try getting over your shyness (easier said than done) but it sounds as if two inexperienced people may have an issue that's hard to resolve.
I know this isn't exactly helpful but I am 20 years older than you and I just don't want you to be still feeling this when you are 50+. If your marriage is great in other ways you might want to stay, but it's something you should think about hard.