How Can I Find Meaning In My Life?
Unfortunately, your questions is one that has no simple answers. Philosophers, Scholars and Religions have attempted to answer this question through the ages. Meaning in life is a struggle that can vary in intensity depending our circumstances, environment, and history. To your point, you seem to be making a lot of negative comparisons to people around you. Although you may not realize that you are doing it, you are expressing that your life just isn't measuring up.
To be honest, there are plenty of people in much worse circumstances in life that would likely feel more comfortable walking in your shoes. I'm sure that doesn't provide you with much comfort, but it might if you take a minute to think about it or act on it. As cliched as it sounds, meaning in life is often directly linked to the people that share our lives. Happiness is not often found by acquiring possessions, completing some career goal, or achieving some milestone. True happiness is finding a way to feel comfortable in your own skin, helping and loving others, and being content with the things you have...not the things you want.
You mentioned in your post that you are not sure who you really are, so I think you might start there and explore that question more fully. Was there a time in your life that you could answer this question easily? If so, why? If not, why not? Self-awareness is one of the greatest feelings a person can achieve. Sometimes it happens all on its own, but sometimes we need a little help to get there.
Helping others also provides a lot of people with a feeling of happiness, so maybe that might do the trick. Often this works because it allows you to experience the joy of helping someone that is experiencing difficulty and make a difference in their lives. Volunteer, be a mentor to a child in need, call an old friend and reconnect, or find something that makes you feel valued by another person.
I hope that this reply can provide you with some thoughts to ponder, but mostly, I hope that you might feel better about all that you have done....not what you haven't done. I wish you well.