Teaching my sons about purity and biblical sexuality

I'm not going to lie, this conversation terrifies me. My oldest is 13 and I know I need to have the talk but make it about more than just biology. I want him to understand why God designed sex the way He did and how to respect women. I was raised in a very repressive environment about this stuff so I'm trying to do better but I feel like I'm making it up as I go. Any dads out there tackled this and come out the other side?