Extreme Postpartum exhaustion

I’m 5 weeks postpartum and within the last few days my bleeding has returned (not heavy, like a regular flow) and I’ve started getting insanely sleepy/fatigued/exhausted, my muscles in my arms get weak, I start to feel foggy in my head and maybe slightly disoriented at times... it’s hard to function during these spells but it usually passes for a few hours and then comes back . I have spoken to my OB and they’re trying to work me in sometime tomorrow for an appointment.. She said it didn’t sound like anemia or a hemorrhage since I’m not losing much blood.. Is there a such thing as postpartum fatigue? I’m sorta freaking out about it because I feel so odd at times but then it passes. Anyone experience this after having a baby?