Yeah, it's crazy how potent the potion of relationships can be, reducing us to an incoherent mess sometimes, as if we've still got all that tween/teen angst balled up in our darkest corners that we only get to touch when we're so so vulnerable... Maybe it's only other people that can reach in there.
I understand some of what you're feeling re: "how can I compete with cock"... It's hard to separate people's superficial (I mean this non-judgementally) preferences for body types/gender etc from their specifically-you desires. It's a complex thing, right? I like reminding myself that I'm grateful to be craved for all that I am, with my bodily manifestation being a temple where my lovers choose to honour me (and, of course, the reciprocal) rather than a more simplistic, physical relationship (which may be great but not what I most desire with my partners.)
If you have some relaxing self-care things you do to affirm yourself (a long bath or whatever) that you have time for before your date, could be good to get into a better mindspace to enjoy the planned time.
Another idea (and this is more twisted, but something I do with emotional bleargh sometimes) is recognising as much as you can about your feelings, where they're coming from etc, and packing them up in a way that can be incorporated into the play (however that works for you). Not sure if this makes sense, but in any case, my thoughts are with you