Spicing things up

Me and my boyfriend have been together for 4 months and we started having sex 2 months or less into the relationship. He waited until I was ready and was very patient about it. He’s at basic training right now and doesn’t come back until December (he called to give me his address, I never got it. He managed to get ahold of his phone last night and texted me the address and told me he loved me and stuff) I get to write him letters but I wanna spice things up when he comes back because it would’ve been a few months since we’ve had sex since then. I don’t usually take my shirt off during sex and if I do I leave my bra on because I don’t like my boobs. I want it to be amazing sex, it’s always amazing but I just want to try something new so it’s more enjoyable for him. I also don’t ride, he’s always on top cause it feels the best for me. I feel like it’s difficult for me to ride I’ve tried. Any advice on how to spice things up and how to ride?