19 with severe psoriasis

Hi everyone, I have recently become covered across my face, front, back, arms and legs with what I believe to be guttate psoriasis. I have had multiple GP appointments but they have said they aren't sure what it is and to wait it out basically. Thankfully I have private healthcare through work and am waiting on an appointment I have booked in a week's time with a dermatologist. I have been off work as it is very painful to live with. The doctor has given me 4 x fexofenadine + 1 montelukast to take daily and has said she is not sure what else to do. My mum has bought me a handheld uvb lamp so I have been trying that for a week now, using it every other day in 20 second doses and slowly increasing. I have also been taking salt baths and I have gone through a 500g tub of cetraben within a week. I have a girls holiday booked for 4 weeks away and I'm just wondering if anyone has any tips at all on how to clear this for then. I feel so lost and it is really affecting my confidence so any tips are greatly appreciated - thank you in advance :)