Blurry vision in left eye while wearing contacts?

I wear my contacts every day. Sometimes, though, it seems like my left eye begins to get blurrier and blurrier all the time. I have astigmatism in my right eye so the right contact is thicker than the other but it doesn't really bother me…

Anyway, whenever I notice blurriness in my left eye, I take the contact out and look at it. It's always dirty, somehow, inside of the lens. In fact, when I took it out and cleaned it earlier today, it was clear for only a couple of hours before the blurriness is back. I really noticed the difference as I was driving home earlier due to the glare of the road signs from the headlights of my car.

Anyone know what can be done to help keep this lens clean or have an idea on how it's getting dirty under it like that? I am due for a contact change in the next few days.

I take them out every night and change them every 15th of the month. I've never left them in for more than 18 hours straight…

Any ideas?

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