Dry masturbation does bring down the sensitivity of genital organs. Dry touching to genital organs, in particular the clitoris is painful and uncomfortable. That comes in the way of orgasm. Further more, too frequent masturbation also brings the sensitivity low. You may take break for few days. Please try with lubrication. Oil based lubricants are harmful to the genital organs. Use only water based lubricants. Vaginal jellies that are available in market are good lubricants. As the time passes, the orgasm goes on delaying. In fact it is a welcome delay since the sex can be enjoyed for a longer period. Also remember, masturbation is a state of fantasy imagination. The orgasm depends upon the novelty of fantasy also. The same imaginations will take away the charm. I hope these answers will solve your problems.