Someone has probably already mentioned this but:
Not being able to thrust rapidly enough (i think it's because i have too much ass muscle or maybe just not enough experience). There's nothing worse for me than hearing "harder" or "faster" while im already going as hard as i can
It can be how you are and her have oriented yourselves spatially. Esp if she's on top and lifting herself up with her legs/arms, thus increasing the linear distance away from the surface against which you are resting to the point of exceeding how high your joints will allow you to articulate your pelvis. This makes it slower (because your muscles have only a given contraction velocity and the longer the distance travelled the longer each cycle takes to complete, as per d=vt.) It also makes it less forceful cause your muscles don't apply a linear force across their entire range, and tend to be weaker at their extremes.
Now, if she is moving herself along with you moving, she can greatly slow it down and reduce the force, if she moving symmetrically with you (That is, if she moving in the same direction as you) it well make it slower and reduce the force, inline with Galilean invariance, in fact, if she was moving in the same direction as you at the same velocity, you would be in co-moving frames and no effective motion exists If she is moving in the same direction, but slower, your proper velocity is reduced and so is the force of your thrusting (because Ke=1/2vm
2) So, get her to move in an anti-symmetric manner and you'll appear to be thrusting much faster, and therefore, much harder as well. (Which can be seen in terms of the 3rd law of motion: The force she applies to you by thrusting towards your penis is precisely the same as the force applied to her by doing so.)
Every man on BL went crazy when seeing your hot body. Not women but men define what's attractive, and you're definitely in 
