Why are my breaks squealing?

I have a honda fit (2015)
I bought it new 3 1/2 months ago and the breaks are already squealing.
I ve driven 9.5k miles in it, most of which are a 100 mile each way trip driving to and from my dad s house, mostly highway, all but 2 miles are 65-80 mph.
I have accidentally left my emergency break on a few times, but never longer than backing out of a space until it dings(I only use the e break on hills so it doesn t cross my mind to take it off or even check)
It s an automatic car, it just started squealing yesterday and it s not every time I break and it s not excessively loud either. It just squeals when I m going slowly and lightly breaking, not when I break slightly harder.

my breaking ranges from very long and slow breaking when a read is about a block or two away to breaking hard due to idiot drivers that either stop too quickly for turns or zipping out of driveways forcing me to stop short. Most of my breaking is average.

I m not sure if it has anything to do with it but it s been getting colder here, below freezing at night, and I park outside in a gravel driveway.

It wasn t squealing when I pulled up to the driveway, but it started when I pulled out, it s never happened before.

I ve heard of breaks squeaking due to dust, but I doubt that s very common.
So do I just take it to a car wash that does the underside, or do I take it to a mechanic?

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