Bi male having trouble with prostate/anal orgasm

I'm not sure if this is the right sub but I posted in /r/sex already and got no responses. I'll just get right in to it (heh). I've never came from an anal orgasm and I'd really like to.I bought this toy this week and have used it twice now. I last came on Sunday from PiV sex with my gf and I used the toy for the first time Monday night and then againTuesday afternoon, both times I dripped pre-cum but couldn't finish. Both times I was super horny and the sessions lasted for about an hour.I used to use standard KY silicone lube but after hearing how silicone toys can degrade from silicone lube I switched over to KY ultragel. Overall it gets the job done but I had to use like a quarter or more of the bottle for one session and it's $11! Is there any other lube that you all would specifically recommend that works better for anal play with silicone toys?But yeah, I also just need advice on getting to the point of a prostate orgasm. I know where mine is and I've tried massaging it with my finger and now this toy multiple times and nothing. I almost always use porn to help me, sometimes with music to give me a little beat even. I've tried it with vibration and with no vibration, I've tried every possible position I could think of. I'm determined to keep it up but I was wondering if there were any tips or something? I don't wanna touch my penis to cum (I'll occasionally rub it for a few seconds just to turn myself on) but after a few more days like this I'm probably going to get gigantic blue balls and will be forced too. It's also annoying because anal prep can take a while and I have to be in the right mood to do it, I also live with people so I don't like to use the vibrator when they're around because it's pretty loud. So what can I do to make this happen?I also do have a GF so I can't go for that long without ejaculating because I still have sex with her. And no, I'm not interested in her fingering my ass, tried it and wasn't a fan. I like her to rim me but for some reason I don't like it when she does anything more, I guess I'm just dominant towards females and submissive towards males.