You're right, I did mis-read, perhaps more that I brushed over it too quickly. I apologise for that. Still you're a winner at 2NL? I'm guessing you make your money because the fishies are calling with weak pairs and draws. And because they are willing to pay whole stacks with a middle pair when you flop a set. Thats going to stop happening as you move up. You're mistakes are going to start glaring at you. You have to realise how important the fundmentals are.. here's some (extremely rough) maths for you..

your stat is 21/7, so you're calling more preflop than you should, say 3% of that is limping hands you should be folding, and 3% is hands you're limp/calling or cold calling. plus you're not raising 3-4% of hands you should be, perhaps a little more..

limped junky hands 3/100 at 10NL $0.30
limp/call, coldcall hands 3/100.. $1.20
failing to raise 4/100 hands, lost the 40c you limped into them

total is $1.90 of leaks preflop.
if you're average to good then you win 4BB/100 hands? which is 80c. but you have $1.90 of leaks preflop so you're losing $1.10/100 already without concidering $ you bust with errors post flop, or even $ you don't win because bet sizing was too big or too small..

Obviously I can't conclude that you're leaks are costing you exact amounts as there's too many variables in the game and I havent even begun to consider that you can win $ when you make mistakes, I'm just trying to illustrate that you've got plenty to work on with just basics and posting HH's. Hell, maybe you're a 4BB/winner as is, fix your leaks cos you might triple your win rate.