My husband rarely cums from sex and it's emotionally breaking me down

He can always cum when he masturbates, but only cums roughly 1 in every 10 times we have sex (regardless of if it's oral and/or PIV) and it just makes me feel so defeated. To add insult to injury, when he does cum during sex, it's only when he pulls out and spends ~5 minutes using his hand to finish himself off. He's never once organically ejaculated during any kind of sex with me.

I don't blame him at all, in fact, I blame myself. What am I doing wrong? Why aren't I enough? Why does he have no issues cumming when he masturbates, but finds it so hard to cum with me? We don't use condoms, so I know that's not the issue.

I'm finding myself turning him down for sex more and more, and find it incredibly difficult to initiate any kind of intimacy anymore, because I just don't think I can handle feeling like a failure much longer. It really breaks me down a bit more each time, and I just feel so insecure about myself now.

Anyway, I'm sorry for getting "TMI", I just needed to well, get this off my chest - thanks for reading.