First off, were you ever winning at nl10, and if so, for how big a sample before your downswing began? Also, how many hands did your downswing last before you dropped back down?
What I'm wondering is whether you were like other players I've seen who moved up and lost more than necessary because they didn't drop back until their BRs got too small to stay.
As for your SB and BB results, what are your vpip and pfr from these positions, and how do they compare with other positions / overall? As others have said, you should be losing money from these seats, but given you lost enough to make you a loser overall, the most likely reason is that you're playing too many hands and/or too large pots with modest hands and usually OOP.
The larger your skill advantage over your opponents, the more you can defend your blinds. However, unless you have proof that you were a solid winner before your downswing began, and also know that you stil played well during it, the obvious course of action would seem to be to defend less.