Why should they think premature ejaculation adult related?
I know It's adult related when you jizz on your pants 60 seconds into watching porn online, but the cure or remedy for it should be in the medical/self improvement related content. If you are having problems with SEO companies being willing to work with you and your project, try to change your approach away from adult for that particular site into a more self improvement aspect and site design.
If you are just too eager to stay to the adult related approach I would recommend watermarking totally explicit sexual videos with your site URL (or shortened link) during your video with a message about how to stop their sexual problems (on this case, premature ejaculation) and upload it to every adult video site you can find.
Yeah, not the answer you were looking for, but it's a secondary way to drive traffic to your site, and a great one I must add.
P.S.: Jokes aside, put more emphasis on the watermark and messages on the first few seconds of your videos for obvious reasons (your niche).