Have you tried to find your gspot on your own?? Try touching yourself to see if you can find it..Once you do, you can walk your husband on how to move in order to do so.
Many women cannot orgasm from penetrative intercourse alone. Your best bet is to have clitoral stimulation during intercourse and that should help you reach an orgasm. There are many ways you can do this. You being on top is a great way, because you can 'grind' your clitoris against him while having sex, also him using his hands on your clitoris during intercourse will help too. There are various toys available that can help this - little vibrating rings that fit around his penis and will stimulate your clitoris are a great way for helping this too.