orgasm trouble

so not sure how to put the title but me and my man have been together. for 6 years. and we have amazing sex. I love it! but when we foreplay and he plays with my clit or fingers me or goes down on me I can never orgasm that way. I usually have to be on top keep in mind that when we have sex I'm completely satasfied. what can I do to be able to orgasm from the for play that we do?