Answered here: https://www.italki.com/question/83458?hl=en-us

My = possessive adjective / Mine = possessive pronoun ( My house is green / That green house is mine.)

To correct your first sentence, for reference: "I have never thought about it." :) As for my and mine, I will give you some examples. "This is my house." vs. "This house is mine." They are both pronouns but are often used in different parts of sentences. Most often, the word "my" comes right before the noun you are describing ownership of, such as "my eyes," "my job," or "my feelings." The word mine doesn't come right before the noun except in really old English (for example, no modern English speaker would say "mine eyes," but you might find it in some old Shakespeare or similar). "That house over there is mine." "My house, my rules!" "That was mine before, but I sold it." <--- Notice how I'm not putting a noun right after mine, like if I were to say "That was my house before, but I sold it."