Bug bites and psoraisis in anal area?

For almost 2 months now, I've been suffering from an itchy butt. There's several spots of what seems to be bug bites. When they occur, they're painful and feel like a pimple. In the inner corner of my anal, I saw that I developed what seems like psoriasis? It's scaly, itches and peels sometimes. They scar really bad to the point where I'm uncomfortable with wearing a bathing suit because you can see them all over my butt. My sister also seems to have it but minus the bug bites. We thought that maybe it was the vaginal wash we were using but we've stopped and it's still there. My dog usually sleeps with me under the covers but I have her on flea medicine. She also sleeps with my brother but he doesn't have any of my concerns. Could it be scabies, spider bites, flea bites or mange? What can I do to heal the itchiness and scarring? What OTC medicine/natural remedies can I do?