Sourdough starter - Have I been doing it wrong? I made my own starter a couple weeks ago: flour and water, and left it on the top of the fridge.  I have been feeding the starter each day for the past two weeks.

I have not discarded any. Now the more I am reading I see I should have discarded half of the starter before each feeding. (Still not clear if that is only the first week or always?)  

For each feeding I used the same amount of flour and water like I did on the first day, regardless of the growing amount of soupy starter in my super large jar.  It has smelled fine, I have even baked with it a few times.

Do I have to start over or can I use this?
You're fine. The reason to discard starter when you feed it is so that you don't end up with exponentially more starter and rapidly run out of room for it. You can slow down the growth of your starter and thus the need for frequent discards by keeping it in the refrigerator and feeding it once a week rather than every day. I've been doing this for about two years now. 

If you prefer, and if you have time, there are a number of things you can make with the "unfed" starter, rather than discarding it. I personally like the pancakes/waffles (same ingredients, different technique) from King Arthur Flour.