I find nothing wrong with what you're doing. It's called filtering.
I don't filter in the middle of cars but usually on the right side which is what I hope you're doing. When I filter, I'm always looking at the traffic light and doors because you never know if someones' getting ready to exit. You have to be very careful when filtering because the law may not be on your side should an accident happen. In fact, the police may very well report YOU as being the cause of the accident.
The "Art of Urban Cycling" states the following on Filtering.
"Filtering to the front of the line comes with certain obligations. The ethics of sneaking up front, past vehicles that arrived at the light before you, suggest that you should allow the trailing vehicles to pass once the light turns green and traffic starts moving again. If there is not enough room for them to pass here, then you should have stayed at the back of the line in the first place. There is really no way to justify filtering up to the front of the line and then blocking the lane after the light turns green.
Even if you have beaten everybody to the light and are rightfully first in line, it may be a good idea to drift slightly to the right, into the void of the intersection, when the light turns green. "
I consider "filtering" a safty technique because you do not want to remain behind a dirty car/bus breathing in all that exhaust. Furthermore, staying in the back of a bunch of cars during a red light does NOT make you safter because once the light turns green, the worse place to be is in the middle of a pack of cars.