? About Brain Mets

I was wondering how most people with brain mets knew they had them. Since starting A/C treatments I have been having headaches and my onc doesn't believe that I have mets. But after my 3rd A/C treatment I had 2 days where I was very dizzy, seeing stars and feeling faint. This went away but on occassion I have trouble with balance, never fell but needing to catch myself when getting up from a sitting position.
I'm see my onc on thursday for my 4th and final A/C treatment and want him to follow up on these symptoms. Fearful that something maybe brewing but don't want to get paranoia either. How does one get there life back after bc diagnosis or does it just become old and you move on? Dx was in 6/05 and still in a state of shock.
Thanks for your help.
Rocky