For me to be able to smell my own body odour, they'd have to be a point in time where I didn't have body odour. And if my BO is so wretched I don't need to put my nose into my arm pit to smell it (I challenge anyone to disagree with me that they don't do an arm pit sniff test to gauge their cleanliness) well, throw me into a fucking lake.
Of course, some people may have more delicate smells than most. Or not at all. I don't know where I sit. But I've got a 100% success rate in never being told 'my dude, you smell like an over ripe peach', so I think I'm doing OK. Or my friends are part of a dasteredly ruse to forever keep me single.
I have a genetic defect where I don't produce apocrine sweat (the kind that causes bacteria to produce odor) but still maintain the eccrine sweat that cools me down.
This trait is associated with dry earwax.
I've worn a shirt for a week straight and had a relative with a sensitive nose smell it and another shirt that had not been worn a day. They incorrectly guessed which shirt I had worn and which one I hadn't.
I can certainly attest that I've known lots of people who seem to be unaware that anyone can smell their body odour, and presumably can't smell it themselves. The keenness of the sense of smell seems to vary a lot more among people than other senses (except perhaps sight, but we use technology to normalize that).
So having known many people who are unaware that they smell, I certainly worry the same could be true of me - I have a decent sense of smell, but probably there are many people who would notice my body odor before I did.