Lindsay Lohan wasn't exactly lonely in rehab, because Breaking Celebrity News has exclusively learned she was seeing a fellow patient while at the Cliffside Malibu treatment center and he was kicked out for inappropriate sexual relations with the actress, but the two continued to meet up outside the center at AA meetings.

According to a former patient who was in rehab with Lindsay — the 27-year-old starlet and a male patient (we are keeping unidentified), the two began "dating" almost immediately upon her arrival at the Southern California rehab center.

"Prior to Lindsay's arrival I was roommates with the guy who ended up dating her. When she came, the first or second day they ended up kissing and it was on from there," the insider told Breaking Celebrity News in an eye-opening exclusive tell-all interview.

"The guy was actually dating someone else in rehab at the time and Lindsay told him he needed to get rid of that other girl and be with her only. She was really territorial with him."

What's more, the insider says everyone in the clinic was aware of Lindsay's relationship with the other patient because they flaunted it — which is what ultimately got him booted from the rehab center.

"Everybody in rehab knew they were dating. It was pretty obvious. But the guy eventually got kicked out because of Lindsay," the source told Breaking Celebrity News.

"The guy who owns Cliffside slacked on the rules for Lindsay, but they got cocky with their relationship and people got uncomfortable with the situation, saying they couldn't do that stuff when people are trying to get well. It was the Lindsay show. Drama.