You've never been the type of explain yourself to anyone, so why start now?
It is your life. You are living your life how you want to. You are making the decisions that are best for you. If they don't approve or have something to say about it that's their problem, not yours.
It's also okay for them to have their opinion, you just can't let it convince you that what they think is better for you. Only you can decide what is best.
They are living their life how they want to live it and not consulting with you before they do so, so why should you have to explain every detail to them?
You are your own person who is strong and can make the right decisions, be confident in that.
Yes, sometimes you need someone's input or a little guidance but if everything you do is based on the opinions of others are you really living YOUR life?
Life is way too short to worry about everyone else. Be happy with your decisions and choices. Whether it is right or wrong, it is apart of your story and it will help shape the person that you are. If people don't accept it, that's okay too.
Once you decide to live your life for you and accept your past instead of worrying about it, your mind will let you free.
The overthinking stops when you decide you're totally secure in yourself and your actions.
At the end of the day, life will go on, with or without them.