The average woman needs twenty minutes of direct clitoral stimulation in order to achieve orgasm, so I am wondering if you are so slow after all or if you are simply comparing yourself with your boyfriend, who, like most males, achieves orgasm much quicker than women do.
The way couples get around this is to make sure that they have a long enough foreplay in which the female's clitoris is quite stimulated before even starting intercourse. A good way to begin is to have him stimulate you almost to the point of orgasm, then begin intercourse. You have a better chance of coming in intercourse if he handles you this way.
As for coming quicker from regular manual or oral stimulation, you can't fight City Hall. Just relax. If you stress out, it will take you longer to come, if you can come at all.
Relax, and let your body go at its own speed. Fantasy, erotic materials, videos can all heighten your arousal and quicken the time it takes to achieve orgasm.
But, above all, remember to relax and take your time. Stop watches are for the Olympics not for the bedroom.