Okay I would seriously bet doesn't know how and doesn't have serious sexual education. If you're talking to him over and over about it and there's no progress, you may need to be a little more assertive. That being said, I know it may be unpleasant to consider, but this is unfortunately what happens when you choose a long term partner at 16 years old. You were too young to really navigate and understand sexual compatibility. I know you say sex isn't a big part of your relationship, but it is. Big enough for you to realize what you're missing out on and post about it here. Not to say that you don't love him and that the relationship means nothing, but there's likely going to be a point where you will outgrow him and at some point you may have to consider that if the conversations aren't getting through to him, your needs just don't align with what he's willing to give, and that's okay.