Unknown mouth rash - please help I'm miserable

Help please.

I've had this rash for 4 months now and no doctor can help. Cortison 1% will clear it but it comes straight back. Starts off itchy and then peels, both lip corners crack and start to bleed and I can't take it till I apply cortisone again.

Discontinued all my makeup and skin care the past 2 months and changed to an sls free toothpaste (sensodyne) and am applying dream cream from lush to relieve the tightness so I can talk. It feels horrible and I don't know what to do anymore. Waiting list for the derm is months away

Help!

Ps I got my bloods taken and all vitamin/ iron etc in normal range