Why do I keep getting headaches?

Usually I only suffer from 1 or 2 headaches a month. For the past week or so I've been having 3-5 headaches a day. The last 3 months have been very stressful for me because my mum was diagnosed with lung cancer that spread to her brain and she has rapidly declined in health.

I know it sounds silly but I don't FEEL stressed. Anyway so I've been to the doctors and they have me strong ibuprofen to take 3x a day. They work momentarily but I'm still suffering with the headaches. Along with the headaches I do sometimes get feelings of nausea, a dull ache in my arms and have moments when I forget what I was about to say. Could it be something serious?