Weatherston was giving evidence, during his murder trial in the High Court at Christchurch, about the nature of his relationship with Sophie Elliott.
Weatherston (33) stabbed Miss Elliott to death in her Ravensbourne home on January 9, 2008.
He denies murdering her, but admits her manslaughter.
Weatherston's former girlfriend, who has name suppression, earlier told the court about a 2006 incident in which he kicked her and jumped on her back, causing a bleeding nose.
Yesterday, he told the court he had been concerned about finance and was worried about his academic future.
He had kicked the woman once on the right shoulder and intended jumping over her, but had clipped the top of her head, causing her nose go into her right knee.
"I felt terrible," he told the court.
Weatherston said he had been prescribed fluoxetine hydrochloride to stop his lethargy after having glandular fever in 2003, but could not recall if he was taking it at the time of the assault in 2006.
He also told of having to seek help from doctors, a psychotherapist and a psychiatrist for his issues with anxiety, the first time being in July 1998.
At one stage early in their relationship, Miss Elliott had produced her diary with a list of 20 things she did not like about her former boyfriend.
Item seven was he was not particularly good in bed.
Weatherston said that after the first time he and Miss Elliot had sex, they discussed things they liked about each other.
"She raised concerns that the things she liked about me were also the things she didn't like about me - that I was attractive to other girls by virtue of being sociable," he said.
He thought Miss Elliott was attractive and had a lot of energy, "not all of it positive", but she could also be jealous, abrasive and insulting.
He told of how she attacked him in bed one day because he would not have sex with her, kneeing, kicking and punching him.
An argument on November 8, 2007, ended when she stormed out, slamming the door and smashing a pane of glass.
Miss Elliott told him about scratching, punching and kicking an earlier partner during an upset, and Weatherston said he told her "there's no excuse for hitting your partner".
"I was kind of enslaved by her a bit", but "I felt I was being appraised by her and having to appease her".
Asked by defence counsel Judith Ablett-Kerr QC about a diary entry in July 2007 when Miss Elliott described him as being "high maintenance", Weatherston said, "I wanted to know more about the person I was getting involved with".
He said Miss Elliott was jealous about his dealings with other students at Otago University and made it clear she had other options than just him; that there were other men who wanted her.
Although he helped her with her university work, she reacted badly when he made a suggestion while she was working at his flat.
She went quiet, finished her work and left early the next morning.
She accused him of calling her stupid and not pursuing the relationship enthusiastically enough, so he sent flowers and a letter of apology.
Weatherston said he also apologised for upsetting her when he spent time with his former girlfriend, who was visiting Dunedin.
"She said afterwards she felt I had not apologised enough."
When Miss Elliott went to Australia on holiday in November 2007, she telephoned him to say she loved and missed him and he told her he did not want to "fight" with her any more.
They made up and the relationship was "unambiguously back on".
She arrived back early from Australia and told him she was going to be much less possessive from then on.
But she declined to invite her friends to Weatherston's pre-graduation party in December, telling him they hated him.
Weatherston said he thought she had been demonising him.
While Miss Elliott was away, he had downloaded material from a website about people in abusive and controlling relationships.
"I thought it described very accurately what I'd been through with Sophie," Weatherston told the court.
He said his former girlfriend's description of "walking on eggshell" was what he felt he was doing in the latter stages of his relationship with Miss Elliott.
He also told the court he was "revolted" by Sophie Elliott's talk of other lovers and the explicit way she gave him details of her earlier sexual relationships.
She described one man having "a penis that was ridiculously out of proportion to his body" and "went on about the different aspects of him sexually", Weatherston said.
It was like she was "almost keen to portray a sexual history to me and we hadn't developed our own sexual history", he said.
