What season did Abby leave in? Did she get married and have a baby with Luka at some point? Someone told me that...is it true? Abby is my favorite character, I'm trying to find out what went on with her from the 10th season until she left. I wasn't able to watch ER after the ninth season so I don't know what happened.

Abby hasn't actually left the show yet although she is quitting at the beginning of the next season. At the beginning of Season 10 Abby is dating Carter but about three episodes in he leaves for the Congo and breaks up with her via a letter. In season 11 Abby dates a medical student (Jake) although this is over by the end of the season. By season 12 Abby and Jake have broken up as have Luca and Sam. Luca and Abby get together and shortly after this Abby learns that she is pregnant. After much doubt she decides to keep the baby. In the Season 12 finale there is a shooting in the ER in which Abby is injured, the baby is born prematurely and the two nearly lose their lives. Luckily they survive and Joe Kovac, their son, is welcomed into the world :) In season 14 Luca leaves to go to be with his sick father in Croatia. Abby goes off the rails and turns to alcohol after her son Joe is hurt in an accident. Abby sleeps with Moretti, another doctor, after a druken night out. When Luca returns to Chicago, she is forced to come clean about the drinking. Luca and Joe go back to Croatia whilst Abby goes to rehab. When they all return, Abby admits to the affair with Moretti and Luca moves out. At the end of Season 14 the two love birds reunite. Season 15 should be starting shortly and Abby is scheduled to leave in episode 3 "The Book of Abby", although the circumstances surrounding her departure are unclear.
Hope that answers your questions :D

Thanks for the info on Abby, I appreciate it :) Would you mind telling me what happened with Carter starting with season 10. I know he broke up with Abby and went overseas and I think got some girl pregnant while he was there and then brought her back to the US?

No Worries :)
Ok Carter....at the beginning of season 10 Carter returns from The Congo to Chicago. However, he leaves a couple of episodes in and returns to Africa to recover Luca's body as he believed to be dead. Carter finds Luca alive and sends him back to Chicago to recover from an illness and pass on a letter to Abby in which he dumps her. We find out later in Season 10 that Carter has formed a relationship with fellow aids worker Kem (played by Thandie Newton). Kem is pregnant with Carter's baby and the two decide to return to Chicago to bring up their child. At the end of season 10 however, their son, Joshua Carter, is born dead. At the beginning of Season 11 Carter proposes to Kem. She declines and goes back to Africa while he stays in Chicago. He has a brief relationship with a social worker named Wendal but is doesnt last. At the and of season 11, Carter goes to Paris to visit Kem and the two decide that they want to be together and plan to live in Africa for good. Carter works his last shift in the ER at the end of season 11. I think he returns for an episode or two in Season 12 in which we see what his work is like in Africa but other than that he is gone by the end of Season 11. It is rumoured that he will return for up to 4 episodes in the upcoming final season though :)