If it is stress-related alopecia, all he can do is offer you meds to calm you down and wait for it to grow back. Patchy alopecia is really common and there isn't a cure for it. It can come once and never return, you can have two patches or ten. But that might not be what the problem is. If you're approaching menopause or your thyroid's underactive, your hair will thin and break (mine did; double whammy) and again, your GP will be able to test you to see what's causing it. Don't panic wildly yet. It could be sorted and grow back again fine. A least it's thick to start with!