Vitamin A and psoriasis

I was about 8 when I first got psoriasis when I was about 15 I got refererred to a dermotoligist and got diagnosed with petipsoriasis and was given a vitamin a cream called differen 0.1% it worked for years until I got pregnant with my son and could no longer use it I'm no longer pregnant mine usually flares up with stress and tiredness but due to having a baby sleepless nights don't help I am ashamed of my skin I didn't let it bother me until it got this bad I'm trying everything just want to know what sort of foods and drinks to stay away from to help my skin :)