Hi Ryan, this is a common problem which 1-3 men face. Too much of your attention is focused on the sensations instead of the actions of performing the sexual act.
Don't know what to suggest regarding masturbation besides slowing down to the point of getting less excited, and then speeding up when things are getting a little TOO slow.
Regarding sex, if your worry is that you ejaculate so fast that your partner doesn't get a lot out of the situation, I suppose one thing you could do is masturbate first, and then start things up with your partner after the refractory period. It should make you last longer the next time (or at least, it's worth trying).
It's kind of hard to answer because "get off quickly" is such a relative term. Do you mean, in 30 seconds? 4 minutes? or what? It seems like as long as your partner is satisfied it should not be a source of worry to you.