You must be referring to the December downs ,
The clinical term - Deerpression
deer·pres·sion
də€RˈpreSH(ə)n/
noun
1.
feelings of severe despondency and dejection, when the rut comes and goes and your phone is blowing up with BBD pictures and you still have a buck tag
"self-doubt creeps in and that swiftly turns to deepression"