how to turn into a losing player that fast!?

[leakmonster]

first of all, hello 2+2 community (my first post)

i can afford croceries by playing .5/1 so i thought "hey lets jump 1 or 2 limits higher and make sum more money". unfortunately, as soon as i jump to 1/2 or 2/4 i cant make a buck anymore. i compared my pt stats with those from winning players and they are not much different. i now lost about 0.02BB/100 over 25k hands on 1/2. i really have no idea where these expensive leaks are, and dont have the feeling that i will detect them too soon. now i wanted to ask for sum advices/suggestions, or even an explanation how this can be, i mean, come on! how to turn from a winning player into a losing player by a jump from .5/1 to 1/2 or 2/4, and how high is the chance that i was just running bad on cards?

thx for any upcommin reply
leakmonster