This is caused by watching pornography. The brain is no longer satisfied with the old videos/images it used to see, and wants to see more graphic and ‘exciting’/shocking material.
You are not the only person this has happened to. It’s not something wrong with you, it’s what’s wrong with pornography and masturbation. When you stop doing it, you will return to your normal sexuality. As you said yourself, those thoughts and dreams are reduced after you stop watching pornography for a week. The cure is no more pornography or masturbation. I highly recommend reading easypeasymethod.org to help you on that journey.
You can read more about this below:
Summary of Your Brain on ■■■■
The brain can be trained to find anything arousing. But the straight men who view this will begin to question their sexuality and feel very disturbed with themselves as a result. Pornography addiction even made gay men watch lesbian pornography. A study of addicts in 2016 found that 20.7% of straight men watched gay pornography and 55% of gay men watched straight pornography. This issue is called HOCD or SOCD (Homosexual/sexual-orientation obsessive-compulsive disorder). Again, this goes away with extended time away from PMO.