One if my mistakes when I was a newbie and didn't care too much about my privacy is using my main email to register on different platforms. I even used the same password 

Many of those platforms were hacked and their databases were leaked. My credentials became available publicly all over the Internet! Then, I started receiving similar phishing emails on a daily basis.
You can use this website to see if your email has been leaked too:
https://haveibeenpwned.com