Say to him that you would like to take it a step further and see what happens. If you really love someone, then you want the best for them. You want them to grow. You are not afraid that they will hurt you. Also, you can disagree without getting insulting.
Sex often diminishes after marriage.
It might be a change in a view of yourself or a change in your view about what sex is supposed to be about. Usually after a slow period, people adjust and resume their sex lives. Forever in love today is largely an illusion. We get so into it that we can't imagine it ever ending. Lots of people find someone that they can spend many decades with.