Even though it was a joke, why does it feel like I'm a failure?

I made a joke to my boyfriend saying I was trans (I mean no offence to trans people) and he said I know, that's why u can't get pregnant. And he knows I have pcos (in one overy) and I want a baby and now I'm crying.

Yes I maybe sensitive. Yes, I'm learning banter. I've been pregnant 3 times (no kids, please don't ask why) this has deeply upset me. I was last pregnant in October I can get pregnant. I don't know anymore :(
Even though it was a joke, why does it feel like I'm a failure?
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