I had an early childhood incident (not rape or molestation) that involved some trauma with penetration. Having penetrative sex with a man for the first time was a big deal for me. I generally am rather reticent about being penetrated, it gives me feelings of a loss of control over my body and its autonomy, and so crossing any barrier like that with somebody (especially for the first time, vaginal sex is basically a breeze for me now) is kind of a whole to-do.