XP in League

Hi,

I am seriously wondering how XP works. This is what I always thought.

Be near enemy minions who die (Killing them does not grant any extra XP).

The reason I am curious, is because just about every game I play, I am always between 1 to 3 levels behind my opponent in lane. Which seems wrong based on the following;

Usually always up by 10 or more cs, this means, I have been around at least 1 wave more minion deaths than my opponent. I'm usually getting ganked in my lane (and most times survive without having to go back to base.). This means that while the lane has more enemy champions in it than I have on my side, their xp should be divided during this time. Most times I am equal with Kills/Assists or have more with less deaths.. But all of this, I am still falling behind in XP. How is this possible?? Please explain. And I do zone control, so I am always near the minions while I force the opponent back.

I just played another game, and this is still true even as jungle, where I share 0 xp with anyone. My opponent jungler had at least 20 less cs than me, double my deaths, half my kills and 1/6 my assist, and yet he was still higher level than me, and they did NOT have a Zillean. Why does this happen, what am I doing wrong, I truly don't understand how this xp works. I also had First Blood, had more objectives than them (Dragons, Turrets, etc.) We did win, but the entire game i was behind levels than my opponent jungler who by every stat on the graph was behind me.