If you cannot find your purpose, maybe the way you look at the world is inaccurate. I cannot say with 100% certainty that "I have found it!" but I did find something new to do that I'm really enjoying. But only after shifting my views to the following:
The purpose of life is simple: to live. That's all. Maybe that sounds a little too simple, but it's actually very profound. Human beings aren't the center of life. In fact, we're absolutely meaningless as far as Earth and even as far as the universe is concerned. One day, there will be no more human beings. This is not good or bad, just the way things are. We are merely insignificant details.
Life, in whichever form, however, will go on. Therefore, to gain the maximum result from our brief existence, we must try and serve the purpose of Life as good as we can. In other words: we must live! Try and get the maximum benefit out of your life. Do whatever it is that you find enjoyable. In the long run none of it will matter anyway, so there's no point in stressing about it. There is nothing you SHOULD do, only things that you CAN do. That is enough to serve Life, and I suppose that is what we call "purpose".
Is this an accurate view of reality? Probably not. But it works for me, and I'm sharing it in the hope that it might work for someone else too.