Well I would love to help you, I really would. That is why I joined this forum.
But I dare not say too much, in case someone feels I am shoving my ideas down their throat or spoon feeding them or boring them or whatever. Blah blah blah.
All I can say is give it time and have patience. It took me six months of diet and then another three months of diet and juicing.
But had I started the diet at the height of my very bad P coverage, I think it would have taken a year. I will never know now, because I know my P will never be that bad again, so I can't test it.
Then again some people clear in a matter of months. Some don't fully clear but do improve: 90% clear is better than 90% coverage in anyones eyes.
I read of someone clearing in 8 weeks after doing a juice fast. Given 7 days is pretty much my limit for a juice fast (and 2 days for a water fast) I doubt I could ever do 8 weeks myself. You can't fast if you are on medication anyway, so fasting is not relevant to you with the Stelara.
It also depends on a lot of other factors (i.e.) work stress levels, home life, emotions, chemicals in skincare, etc... diet is only one factor of a bigger picture.
You may get worse before you get better, or you may have a slow steady clearance over several months. You may (as in dieting) hit a platitude for a while and if you do, you may need to fine tweak.
Try to be strict in the first 3 - 6 months, as constant yo-yoing between healthy food and unhealthy food is very detrimental. And you may actually undo all the good work you have done.
Remember things have to work on a cellular level, before the results will show up on your skin. That is why patience is required.
No doubt I have said too much already, so that is all I will say.
Good luck with it all.
Maybe send a PM to Lazza, as he one of the most helpful and knowledgeable people on this forum.