WASHINGTON (Reuters) - When Erika Eckstrom began dating her boyfriend at the start of her College freshman year at 18 things were great, but her situation deteriorated and she soon was friendless, isolated and the victim of domestic violence. "Everything was great and when it started really getting bad I don't know if it was denial, but I knew something was wrong, because I was without a support system," said Eckstrom, now 20 and still in college in Washington but dating someone else. Her story is apparently common among teenagers. According to a study released on Thursday, more than half...