When my orgasms start slowing down, I usually switch techniques/toys or introduce a new element, or use something I haven't in a long time. Vibrator not doin' it= time for a shower massage.
I don't know if you've tried all this already, I'm pretty easy to please.
it's all in the mind. Teasing yourself by watching an erotic movie, reading erotica or fantasizing about sexual acts long before you even touch yourself could possibly do it.
Experiment with different lubes. I like Liquid Silk the best, myself. It could definitely be worth your while to get some sample sizes of lots of different ones. I can make myself come approximately 324% faster with lube than without, and that percentage increase is definitely lube-type-dependent. Don't just settle for any old lube. Find a favorite.