Psoraisis or Yeast Infection? Treatment?

Hello

I was told by my GP about 2 years ago that I had a yeast infection in my anal passage and around my groin area.  I also have dry skin in my scalp and behind my ears.

For the past year a few of my joints have been swollen.  After much investigation and having seen a rhumatologist I was diagnosed with psoriatic arthritis, even though I have never been diagnosed with psoriasis before.

Could it be the case that I don't have a yeast infection at all and by applying canesten hydrochortisone on and off for long spells I have caused mre damage than good?

I feel that my skin is deteriorating, online I cannot seem to find much help as how to tackle psoraisis (psoriasis) that is in the inside of my anal passage.  It is quite discomforting and I would like to get something sorted

thanks