That combined with what you mentioned about cannabis triggering your headache sounds like the issue might be your trigeminal nerve (my guess mylohyoid) or similar nerve branch in the neck area. Sleeping likely causes it because there's constant pressure on it at night as you sleep.
Alternative hypothesis would be it's blood pressure related, perhaps orthostatic hypotension or fluctuating hypertension - you can test this by getting a good blood pressure machine and checking in the morning before you get up from bed without moving much, immediately after sitting up, immediately after standing, and then stay standing still for 1 minute and take again.
Probably don't need the coffee by the way considering the medicine you take (Ritalin)