Other than learning to relax and not to worry so much about orgasm and more about enjoying your bodies (Not to make that sound like a negative) there are a few things that you can try.
Sensation lubes like warming, cooling and tingling may help with, well, sensation. It might also be worth having him masturbate using an oil type lube. I find that sometimes if my penis isn't feeling as good as it could, using an oil like vit-E oil makes things more supple and restores a bit of feeling.
Another thing to think of is to focus on other places of the body. Nipples can be very, very pleasurable, as can scrotal, perinnaum stimulation, If he is willing, anal and prostate play can be astoundingly good. The belly button and the section of skin between it and the crotch can also be very nice to have stroked. I suppose that that isn't unreasonable, because I'm sure any guy can tell you that if we are ever hit in the balls, the pain goes right through your stomach. There much be some sort of nerve connection going on there.
General massage could be good, along with sensation play with vibrators, feathers, ticklers, wartenberg wheels, ice cubes and even candle wax, floggers and other BDSM tools if you are open to it.
Having him blindfolded may aid feelings aswell, as the unexpected nature of it can make things feel more pronounced.
Really, anything that generates a pleasing sensation can be added to sex to increase pleasure. Using tools, toys and s&m gear might seem a little intimidating but the intention behind the act is more important than the tools. Using a flogger or blindfold doesn't require any form of power play in oder for them to be used, and can instead be a way of purly increasing stimulation.