Breast dent

I am a 35 mother of 2. Now 10 ... and 2... Breastfed both for approx 6 months. My breasts are fairly large, and i am not a petite woman. I was doing a self breast exam one evening that led me to believe something felt "wrong" when in fact i think it was regular tissue and fat . It set me into a spiral of googling and somewhere i read in front of the mirror to flex. If you do this and there is a 1 sided dent... it is potentially a symptom of breast cancer. Low and behold i do dent when flexing. Left side only . horizontal about an inch long. Not there when i hold my hands above my head... and seems to be more prominent at certain times.. though that could be completely in my head. I went to a dr. As i convinced myseld i had numerous symptoms. And although she seen it, and did a breast exam she commented generally dents they look for dont appear in such a manner. They usually look like they are being pulled in (to me i cant understand the difference) and images ive seen look similar to me . My grandmother on my maternal side had breast cancer , so for covering bases she referred me for a mammogram followed by an ultrasound. That is coming up this monday (2 days) and i am worried sick. That she actually does suspect something. That that dent is in fact indicative of something sinister and that my life will forever change .
Google clearly tells me nothing but the worst, and i am reaching out here in hopes of having some reality brought back into my mind.
Thanx in advance

Your Dr is doing the right thing sending you for a mammogram and u/s. It will be a base line so you know what to expect when you do your monthly check. I had my first mammogram at 38 as I had lumpy breasts, so I found this very useful. I'm sure you will be fine :)

I have have a dent on my right breast that appears when I lift my arm. Noticed it 4 years ago. Had all the tests including a breast MRI because I was petrified. Dr wasn't concerned, said it was a lazy ligament. Tests were all clear. It's still there, still the same.