It’s pretty common for some women to pee during sexual stimulation if they’re very turned on. Do you find anal sex to be quite pleasurable? Some women do, apparently it’s possible to stimulate the g-spot, which can cause the so-called ‘female ejaculation’. If you’re enjoying this & the only issue is the peeing, just put some towels down. I would say this could be considered ‘normal’ for you, maybe not for everyone, but wouldn’t consider it abnormal at all...