Private practice question about Charlotte and Cooper?

Apparently Charlotte had been married before and she was in love, then she told a patient, violet overheard and made Charlotte tell cooper when cooper found out he was hurt charlotte hadn't told him, and assumed that she was never really IN their relationship.

He found out that she had been married before and lied to him about it.

Just to add to the first answer by I Love Vampires, Cooper is also upset with Charlotte because he feels as though she doesn't have the same emotions as most humans do (or she doesn't share her emotions) and I think it really pissed him off when Charlotte shared a secret with a patient but not with him. He doesn't feel like Charlotte is emotionally involved in their relationship like he is. He thinks all she wants is to have sex and emasculate him.

Starting in season three, Cooper's relationship with Charlotte is rocky. Cooper is upset over Violet's attack, and Charlotte is upset after being called heartless. In episode 3x3 Cooper sweeps Charlotte off her feet and brings her to live with him. In the next episode, Cooper's financial issues catch up with him when he needs to buy out part of the practice. Because he doesn't have the money to pay for it, Charlotte buys Cooper out and asks to join the practice. She is admitted in, and she changes her specialty to sexology. Cooper is very uncomfortable with this. On numerous occasions, he insults Charlotte's work. It is soon discovered that Charlotte was married before and the marriage ended badly. Cooper is very angry that she didn't tell him sooner.

In episode 3x8 "Sins of the Father", Cooper is arrested after hiding a runaway child and his father from the law. The kid claims to have been abused by his stepdad, so his father came and took him away. Cooper is released when the father is found and put in prison. Charlotte is treating the kid when she finds out that he was lying and there was never any abuse. When she tells him this, Cooper yells angrily at Charlotte about how she has been lying to him. Cooper is unable to forgive Charlotte for not telling him about the marriage, and she still won't tell him why it ended.