If your penis continues to feel irritated and itchy, and you have been good at cleaning it and maintaining proper hygiene, a visit to the doctor is in order. It could be any number of things, including just a simple allergic reaction to the kind of soap you are using or the laundry detergent used on your clothes, or that the clothes you wear rub your penis the wrong way. One thing you should do going forward is to regularly apply a penis nutrient cream (health professionals recommend Man1 Man Oil) to help reduce itching and redness and to keep the penis moisturized and the penile skin from drying out. Take good care of your penis and it will take good care of you.
Well, take some long bath soaks, but if it does not clear up, you should see a doctor. If you were drunk to the point of not knowing that someone was handling your body, let alone your penis, there are a lot of things that could have damaged it. I would also talk to the doctor about drinking to the point of blackout. Not just red penises come from doing that.