I’m sorry you have been suffering so long. It’s long past time for you to get some help.
Obsessions like you describe are part of the Obsessive Compulsive Disorder (OCD) spectrum. Yes, it’s possible to have obsessions without compensatory compulsions. Some people, like yourself, have repetitive, intrusive, unwanted thoughts but do not find relief by engaging in a particular behavior in an effort to make it go away.
Obsessions can dominate someone’s life. Even when a person knows they are irrational, obsessions usually don’t go away. They often feel impossible to control. In fact, trying to control them may even make them worse.
You already have some guesses about what may have triggered the content of your particular obsession. Wishing for a more nurturing mother, you started fantasizing about women who might fulfill that role. Then, somehow, the harmless wishing transformed into an all consuming obsession.
But, as you’ve found, having an idea of the cause doesn’t get rid of the problem. For that you need to see a mental health professional for some treatment. Cognitive-behavioral therapy has been found to be very helpful. Some medication may also help relieve your symptoms. People usually respond very well to focused treatment. I hope you will do yourself the kindness of making an appointment to start working on the skills that will give you relief.
I wish you well.