What should an unmarried woman who has frequent, unexplained sexual urges do? The Prophetic advice of fasting does not seem to be working in this case.
Depends on whether you have a mental illness. I have bipolar disorder with hypersexuality that comes from the bipolar. Fasting didn't work, neither did simply praying or any other method that was prescribed. I've started taking medication and seeing a therapist. People make it out to be a joke and in reality it is very real, very damaging, and a very painful process. And being a hypersexual destroyed my marriage, so it wasn't about "getting married" because I was . What many don't understand is that those with hypersexual disorder are never satisified unlike those who are not inflicted with such mental disorders. But alongside medication; therapy; then we must also strive to read Quran, fast and pray properly. Having a mental illness doesn't exclude us from struggling and striving towards Allah. We just have to fight the nafs just a little harder in shaa Allah.
1) get married
2) become the second wife of a man who who is already married
3) keep fasting - but only eat a date or two at iftaar. The prophetic advice of fasting is aimed at causing hunger. This sustained hunger, over many days, will reduce the urge. Thus, reduce your food intake to as little as possible. Your urges WILL slowly die down, though they may temporarily increase
except fasting, u must control yr eyes. they have the most important role in controlling yr mind & heart( u must even control yr eye at pictures & movies) u can read ayeh 74 of surah forghan(25 of quran ) in yr qonuts & after yr prayers (والذین یقولون ربنا.....) u can give sadageh daily for this especial intention( we have hadith that u can control yr nafs with sadageh!!!!). u can have tavasol to ahle bait especially to imam java pbuh for this especial problem. he helps to young people in getting married.
These conditions fall under the umbrella term called "Addiction", and has something to do with your Dopaminergic activity.
Are you sure fasting did not help?
Food Restriction Increases Dopamine Receptors. ...The scientists found that genetically obese rats had lower levels of dopamine D2 receptors than lean rats. They also demonstrated that restricting food intake can increase the number of D2 receptors, partially attenuating a normal decline associated with aging. (Source)
For a complete overview and further details about the receptor control theory, I strongly recommend you to read this especially the section "HOW TO UPREGULATE YOUR RECEPTORS".
Fasting (includes cutting sugar and not overeating while not fasting) with essential nutrients.
Exercise as much as you can.
Finding other ways to maintain the high.
Please do follow the above tips, strictly.
Note: Don't just try to increase Dopamine.
(Revision Before Edit)
Please note that usually the symptoms like compulsive paranoia / hallucinations (which you've been calling vivid imagination a.k.a day dreaming), and addictions are related to serious mental disorders like Schizophrenia, Bipolar Disorder etc. These thoughts come again and again, no matter how hard you try to not think about them.
Well for sure you can follow the Prophet advice of fasting, but while you're not fasting you're obliged to consume healthy foods with Omega 3, B Complex etc.
Apart from that, meditation and jogging / exercise helps you control your thoughts. Get new experiences, learn new skills, memorize a new Surah etc. (proven to increase gray and white matter of brain). Also often suggested is cutting down sugar and having whole grains in diet.
Marrying is not only a solution, but is a Sunnah (but it won't likely solve the problems altogether).
If the above advises are not a solution for you, then maybe visiting a psychiatrist would be.