My T says this does happen to some people. I will tire myself out with worry and anxiety and then become depressed for awhile. She even gave me a diagram once to show this. It started out with the Fight-Flight snxiety feeling with adrenaline release etc. Then the body releases neurochemicals that drops you into decreased heartrate, exhaustion, increased gastro activity, depression.

She had another diagram that called it Hyperarousal vs Hypoarousal.

Hope you feel better soon