Focus on the pleasure only. Breathe deeply and slowly. Try to be more gentle and act erotically towards your ass and prostate. It took me about 10 years to have a hands free prostate orgasm. However, these all came without a cumshot or traditional finish. I thought a "prostate orgasm" involved cumming, traditionally, from my penis. This is not how it works at all. Some guys have prostate Os and their cock cums too. Some get hard while anal stimulation and prostate Os happen. Some stay flaccid. Some can only have prostate Os if they are flaccid. Its a mixed bag man, it just has more to do with what the feelings feel like and if you can identify them as "that is certainly my prostate" or "wow, that makes my anus contract uncontrollably, which is driving/altering/affecting the toy in me that is making the contractions happen" then you are on your way to hands free prostate orgasms. Out of the thousands of prostate, hands-free Os I've had the last 10 years, I've only had 2 where I came like for real, my cock was hard all on its own and the Aneros autofucked me until I was shooting cum all over myself. Just twice that happened and within a week of each other. Its been 7 years and it still hasn't happened again, but all the other Os I have are worth not having that cumshot hands free O.
You have to give in to it fully. But not a pushing kind of giving in, like the "peeing" feeling you brought up, I seldom feel that when I have prostate Os. If I'm milking my prostate purposefully, it feels like cum is slowly trickling out of me, or like a "ball" of it is rising ever so slowly towards the tip and when it finally comes out its like a drop sometimes, it feels like a full on orgasm with cumshot. My usual 30-45 minute prostate sessions involve a handful of toys that are Aneros and related style toys, gspot dildos, and realistic dual density silicone dildos. I have to do different things with each to have prostate and anal Os. Some I just lay there and they happen. It is normal for me to have an orgasm within sometimes just 30 seconds or a minute after inserting the first toy of a session. But within that 30-45 minutes I have countless orgasms, easily over 30 during even the sessions when I felt like things weren't going so great or I was distracted from life stress. Most decent and good sessions I'll have 50+ Os around the 45 minute mark. If I go for an hour or longer its serious, a fuck machine is involved, and the Os are beyond countless. Some Os last about 20 seconds, many are just blip type ones that last a couple seconds. But my ass and body are having an O. They sometimes feel like a wave passes through and over me, like an EMP was set off somewhere and the shockwave blows through me. My cock is usually flaccid or I have a semi during my whole session. I never ever touch it until I'm done and want to finish with a super T or a traditional penis-oriented orgasm and ejaculation but I have a toy in me while doing it. That's the mega finisher, the Mortal Kombat fatality and flawless victory, the last shot before leaving the bar.
I never ever watch porn before or during a session. I don't watch or use porn at all anymore, but when I did, porn never came into a session with me. I use the routine of cleaning out and preparing the space and all my toys as a mindfulness practice and I clear my head of expectations and the noise of life. Porn distracts too much and its penis-oriented in our usual self pleasure play and anal and prostate stimulation and orgasms stem from a different place with different stimulation.
Don't expect a cumshot-type orgasm. That's what I did for 10 years and I got nowhere. Finally when I just decided to give into it see what the stim all felt like for real, fireworks went off and I have never been the same; that was 10 years ago. You will get the orgasms you crave and hope for!! They're easier than you think just don't try so hard and try lighter stimulation for longer. You got this!