This happened to me with Moderna vaccine #2. I had bad headaches from day 3-12. By 13-16 I saw it significantly decline. I am on day 17 and now doing almost 100%. The worst was days 3-7. My doctor did blood work and everything came out fine.

You are very likely going through what I had which is a STRONG immune response that causes some inflammation. The GOOD news is it will go Away. It will just take some time. I urge patience. Hydrate. Sleep a lot. Take naps. Reduce stress. Reduce screen time.

Of course if you feel the urge go to your doctor's. But they will likely say same thing which is you had a strong immune response. BTW. I NEVER get headaches so this was also strange for me also. Message me if you have any questions