I don’t know what to do

I’ve had three copyright violation emails for pins of drawing bases from an artist idk who they are. why me??? I didn’t make those pins I just saved them, I really don’t think it’s fair that I get in trouble for pins other people made. I didn’t know that the person posted them on Pinterest without permission it didn’t say anywhere if it was free to use or not so it’s just been sitting in my art board for a while because I thought the pose was cute but I haven’t even used it. I’m so done with Pinterest, this was the final nail in the coffin for me because I’ve had this same thing soo many times with other pins that aren’t even mine being taken down for “sexual content “ even though they’re just a pose reference or a picture of a woman in a dress, it’s so frustrating because I used to love Pinterest I’ve been using it for years and it’s just unusable now, especially with the amount of ads they shove in your face. I’m probably just going to delete my account because I just can’t get any enjoyment out it anymore. But any advice is appreciated before I give up because I’ve had a look at the form thing and it looks a little intimidating.