Hello and welcome to the forum. Sorry you and your mother both are both feeling so poorly with headache and fatigue. Seeing a doctor is always the best thing to do. In thinking about chronic fatigue syndrome, headache and fatigue are on the list of symptoms among other things. It's normally caused by viral infections, immune system problems or hormone issues. That you and your mom both have this could possibly be a viral infection? Here is information on CFS https://www.mayoclinic.org/diseases-conditions/chronic-fatigue-syndrome/symptoms-causes/syc-20360490
Other things that cause the symptoms you describe are dehydration, low blood sugar, sleep disorders or anemia. Anything like that possibly going on?
There are many diseases that can cause headaches and nausea, such as chronic fatigue syndrome, encephalopathy, mental illness, and so on. Frequent headaches and nausea may also be caused by cold, overwork, and poor rest. You need to go to the hospital to do the relevant medical check to determine the cause. After the diagnosis, you should follow the doctor's advice and your condition will gradually improve.
If both of you are feeling that way is there something you are both exposed to? Drinking the same tap water maybe?