Sensitivity to light often means sensitivity to ultraviolet light which is a yellow flag for many illnesses, specifically Lupus.
You need a work-up from a physician.
Sleep deprivation definitely has something to do with it, though this sounds more like migraines or daily headaches. Your sleep/wake schedule is controlled by a small gland attached to your brain--the pineal gland. It releases a chemical that makes you sleepy, melatonin, based upon your exposure to natural light. If you have a messed-up sleep schedule or you aren't sleeping long enough, this can easily cause hormonal disturbances and make your body "confused" about why it is awake when it shouldn't be, causing problems like headaches, brain fog, and fatigue.
I would recommend that you try to avoid being sleep-deprived in the future, if possible, and consult a doctor on treatment for postnatal depression. Depression can cause different types of sleep disturbances by dint of it affecting important neurotransmitters in your brain. Treatment of this will likely help stabilize your sleeping patterns.