IPhone 4S camera has been taking bad quality pictures?

I've had my phone for a year now and the pictures have always been good until like a few months ago. Now they are just super bad quality and I even have used camera plus to try to make it look better. Do I just need to clean it (if so, how do I?) or should I take my phone apart and look inside and see if there's dust on the lens?

What's wrong with that pic?

Well, my first instinct would be to say, "It's a phone, don't expect much", but since you say you can see a marked difference lately, there's obviously something that has changed. Looking at that photo, it does have an overall lack of contrast and sharpness. My first guess is that, yes, the lens needs cleaning. HOW that is done on your device I have no clue, but I would not think you would have to "take it apart" to clean the lens. Get some lens cleaning liquid, put a SMALL amount on the end of a Q tip cotton swab, and carefully go over the outside of the lens. Then use the dry side of the swab to be sure there's no cleaning residue on the lens.

I don't know what else to tell you.