What's wrong with my eye?

I'll be honest, I'm not the best when it comes to taking care of my eyes. I started wearing contacts four years ago, I don't usually wash my hands before I put them in or take them out and I change the contact cleaner fluid in the case once or twice a week. But I've never really gotten a serious infection. Lately though, at the end of the day, ONE of my eyes (it switches) will become very bloodshot and kind of a clear, gooey, film covers my one eye... it's very gooey and when I rub my eye t goes into the corner... it's either white or clear. My eye sometimes burns or stings but it's weird how it's just one eye and it switches. It's usually only like this for one or two days and then goes away for a few days or a week then happens to the other eye. What can it be?