Plus Size Riding

So my boyfriend used to mention how he wanted to be ridden (he said this before we were together) and I want to give him what he likes, The only problem is I’m on the bigger size and I’m super insecure. I feel like I’m gonna crush him or make it uncomfortable for him. I also just don’t know how to be on top. Any tips? I should also mention he’s a lot smaller than me, still muscular.