While it is primarily designed for analysing feelings about a partner, the app allows users to colour-code how they feel about any relationship in their lives and can track multiple relationships at once.
As each day goes past, users write down significant events that happened and colour-code the day. For example, green stands for amazing, orange for happy, while blue and red represents sadness and anger within the relationship.
The idea is that over time, even if someone is willing to forgive and forget problems within a relationship, the app will show whether the romantic partner is actually having a positive influence on the user's life or not.
Breaking patterns of co-dependency
In September 2007, Sivertsen's husband left her after 19 years, and she realised she needed to get her life back together.
"Before my husband left, all I wanted to do was hide in my house and write with my cats and dogs. I had this quiet life. But when he left, I felt lost. I had never paid for anything by myself, but I had to. So I had to scramble as I needed to put my 17-year-old son through college," she tells IBTimes UK.
Sivertsen realised that her biggest problem was that she had been co-dependent, a psychological condition where people place a lower priority on their own needs compared to those of their partner and become passive and too forgiving in an emotionally or physically abusive relationship.
According to charity Women's Aid, in the UK alone one in four women is a victim of domestic violence in their lifetime. Even if the abuse is "only emotional", its impact can have much longer-term effects than physical assault.
"I kept a diary [about] my husband and I would make entries when he gave me clear indications that he was unhappy. But when he apologised, I would feel guilty and delete the diary. When my husband left me, I realised that no amount of self-help books and seminars were helping me to break my habit of co-dependency and I think my sister and therapist were tired of being on speed dial, so I started keeping the diary again," she says.
Sivertsen continued to keep her diary, mapping out her feelings day by day so that she would not need to talk to other people to figure how she felt.
"I got married at 23 and I thought that I would be with that guy forever. At 43, I found myself single, wondering if it was too late for me and if anyone was going to want my sorry ass. I needed to become my own best friend."
Three relationships, not one
Her idea proved so successful that her assistant started doing it too and had good results. Eventually in March 2013, after feeling settled in her own love life, Sivertsen decided that her idea would be good to share with other people.
She found an app developer to work with her. The app took five months to produce.
It is not just a diary though. Sivertsen and her team will continue to add interactive functions so if a user had a bad few days, the app will send the user a push notification alert on their smartphone, asking them if they would like to consider asking for outside support.
Sivertsen is also compiling a series of free relationship advice articles by prominent dating coaches and relationship advice experts such as Arielle Ford and Evan Marc Katz.
These articles will be free to access on the Boyfriend Log website and are designed to act as a companion to the app.
Three hundred and fifty-nine people have downloaded the app since it was launched less than a week ago. Based on feedback from beta-testers who used the app for a month, some couples use it together to better understand their relationship problems.
"Every relationship is really three relationships: The one you're having, the one he's having, and the real one," she says.
"About 20 years ago when I got into the self-help field, people were saying that online information is going to be the new way [people wanted to receive help], but now I'm hearing that mobile apps will be the new way."
The Boyfriend Log costs £1.49 or $1.99. An Android version is in the works, together with the Girlfriend Log app for men.