I think it’s possible that your unhappiness is a way you are telling yourself you need to make important changes in your life. I understand why you are afraid to leave a good job. But you said a very important thing in your letter: You said you have limited skills.
I imagine that as an administrative assistant, you do have skills in organization, word processing, and managing tasks. What you don’t have are the skills you need to put them to work to advance your interests.
My advice is that you start taking courses at your local college that are compatible with your dreams. Have you thought of the hospitality business? How about cruise line work? Or maybe you’d like to work outside your own country for a few years (in which case, you might need to learn another language).
Start with one course you can take during evenings or with workshops that happen on weekends. Taking some positive action and being around classmates who share your interests will probably give you the push you need to start feeling better and in more control of your life.
I wish you well.