how do I get my husband to be more aggressive?

My husband and I are thinking about trying new things. I asked him what he would want and all he said is more blowjobs, fair enough I can do that. He asked me what I wanted I told him I would like it if he was more aggressive, like come up behind me and just take it occasionally lol. Sounds freaky sorry if it's TMI. His reply is he doesn't think he can do it. He blames it on him being a "loser" in high school and how he didn't have a gf till junior year and also on his sexual harassment and rape prevention training he's had. I just want him to try at least once see if he even can cause our sex life has become very basic and not fun anymore >.< and I love my husband and want to be with him just I need some spontaneity. Any suggestions on how to get him to loosen up or any suggestions on new things to try?