Hey there littlesaphire, and welcome to the boards
I’m sorry to hear that you’ve been having lower back pain after masturbation. I want say, first, if the intensity of the toy is causing you pain, it’s okay to turn down the setting (if possible) or not use it. There’s not a toy out there that feels perfect for everyone who uses it, and it can take some exploring to find a toy with the right intensity, so if it ends up being that this toy is just too intense, that’s okay. But if the intensity is a part of the pleasure, I totally get that, and we can talk about ways to alleviate some of the pressure on the lower back.
So, just as there’s not a single toy that works for everyone, there’s also not a single sex position I can recommend that I know feels good for everyone or that people’s bodies react to in the exact same way. That’s why my best advice for this is to experiment with different positions that you can think of and see what feels good for
your body. That being said, I do have some ideas about general positioning and aids that help folks with pain. If it hurts to lay on your back, the simplest idea is to lay on your stomach instead and see if that alleviates some pain; you could also try sitting down, laying on your back but bending your knees to your chest, or laying on your side. Another thing that might really help here is a wedge pillow, or any stiff pillow or rolled up blanket or towel really. They’re great for positioning the lower back while laying on your back, and it puts a lot less pressure on the lower back. If that’s something you could get, it might be worth exploring with! How does all that sound to you?