That's whats called the start of "Yer Mid-Life Crisis" Kev. And it happens to the best of us, so don't worry too much, unless it's something that's making you genuinely depressed.
Thing to remember is, you can't go back in time and 'un-waste' everything you consider wasteful. The past is the past, what's done has been done. The trick is not to dwell on the past too much, move on, and start living from the here and now.
Try writing out a list of all the things you'd really really like to do or achieve in your life, then start making the neccessary plans to do them, then, just do em. Have a good long hard think of the things in life that you consider worthy and fulfilling, then, as long as they're legal, point your life in that direction and go for it.
This is gonna sound really trite, but, if you're searching for true happiness and true contentment, then you'll only find it in one place. And that's in your own heart. If you're comfortable in your own skin, then you never have to live up to other peoples or even societies expectations of yourself. Learn to love yourself first, then you'll find it much easier to love the life you live. And don't be ashamed of who you are, whoever or whatever you are.
But, it's important to set yourself goals, something to reach for, something to attain. Otherwise you might as well curl up into a ball and die. A man without hope is well and truely hopeless. But if you're aware that things aren't quite right, then change them. Its as simple as that. And you are the only one that can change yourself, no one else can. It's up to you !