That should've been SKINS (UK). At least the first two seasons, I didn't watch the next yet. I don't plan to, though, so they feel pretty much completed.
The last one I "really" completed was Teen Wolf. :P
There are actually a few I marathon watched at the same time. Season 2 Game of Thrones (started season 3 last night!), Seasons 1 & 2 of Teen Wolf and Awkward.
Gossip girl season 5, Pretty little liars season 1, Sex and the city season 5
Currently watching The Vampire Diaries, Dr. House, Grey's anatomy, Desperate housewives and most favorite one is FRIENDS kkk