For yoir PC, also try using the 127.0.0.1 to block websites you ised to go on for porn. Just go in your ‘hosts’ file in local hard disk, open the file with note, write 127.0.0.1 thenameofthewebsiteyouwanttoblockhere on a new column. This technique is great if you use windows.
I also use an android device and searched long for what you ask here, but never found it (even though I know a bit about programming and considered even rooting my phone). So honestly, I just disabled google chrome, appstore and youtube from my phone and I’m so much better off. I would really do this if I were this, you will have a lot more free time for truly important things, and you will eventually realise that all that internet thing was not even meaningful to you.
This seems quite radical but believe me, it is the only good way I know of.
Good luck anyway, maybe you will find something perfect for you.