How common are sexual side effects?
According to the FDA, in clinical trials, 1.2% of men discontinued finasteride due to sexual side effects, compared to 0.9% of men taking a placebo. So if the same percentage of men in the finasteride group also incorrectly attributed side effects to finasteride, then the total proportion of men who stopped treatment would be only 0.3%. (Source)
What’s happening in my body?
When you increase your testosterone, as with testosterone therapy (trt), you always increase your estrogen slightly. That's just how the body works because some testosterone is always a aromatizing into estrogen, so more testosterone means more estrogen. So perhaps you were an uncommon case where the increase in estrogen affected you negatively. According to the FDA, approx. 0.3% of men stop taking finasteride due to sexually adverse effects that are possibly or likely drug related.
Is finasteride causing my ED?
18.4% of guys in the US suffer from sexual dysfunction like ED and loss of libido without taking finasteride, so it is very difficult to determine how finasteride is affecting you except for in a controlled clinical trial. Every double-blind placebo controlled trial (clinical trials that eliminate bias) has found a very small or nonexistent percentage of men with sexually adverse effects from finasteride.
Does sexual dysfunction go away?
For men who never take finasteride, sexual dysfunction can last for months, years, or life. ED is nasty and not relegated to something caused by drugs.
According to Harvard Medical School, some men report persistent sex drive and ejaculation problems after stopping the medication. This is not proof that finasteride is to blame, since a variety of medical conditions and other prescription drugs could explain the sexual symptoms.
