Since you quit Fluoxetine 2.5 years ago, and you were only on it for about six months, it would not be a factor now with your current erection problem. Your doctor said you have a low sex drive. Do you think that you have a low sex drive? If not, your ED could be caused by side effects of your current medications. Of course, do not stop taking any prescribed meds, but check with your doctor for any alternatives that would not have the side effects.
The cause is without a doubt the fluoxetine. Low doses would cause light problems and as soon as I stopped the problems completely went away. But then the doctor tripled the dose and then the problems became much more severe and permanent. I do think that my sex drive is low, even though I want to have sex and masturbate but when I try to do it I have problems with my erection.
I still think that your erection problems are at least partially due to your current meds. You may have a low sex drive, but it's still a sex drive, and you want to masturbate and have sex with a partner, so I don't think all your erection problems can be tied to a "low sex drive". As mentioned before, you don't want to quit any meds on your own, but hopefully your doctor could come up with other options. If you do get a partner, I recommend stopping all masturbation and use of porn while your relationship continues.