Maybe it's the way I do relationships, but in all my good relationships the girl and I slept together within the first few dates. Maybe because my life is very chaotic & complex so I pickup on girls with simaliar experiences, but I take my time and focus with her in the sack, so the relationship is born.
As for the trust, sex to me is a great measure of trust. The girl trusts me to put herself in such a vulnerble position both physically and mentally, and I put the same trust in her. No trust = No sex.
But that's just my oppinion. I could be wrong.