Experience and Mordekaiser problem I have had

First, my experience was 980/980 and I did not level up. I thought maybe it was because I died but I didn't level up when I revived. I didn't level up until I killed another minion. This only happened to me once. But this is also a rare occurrence that this all lines up so I wanted to report it. The Mordekaiser problem I've noticed is that his ult isn't stealing health like it says. The only time I get any health from the ult is when i have spell vamp, so I'm not really getting any health from the just the damage.