Thank you for your question.
I understood that you have been using the propecia/saw palmetto 8 years ago when the symptoms started. Are you still using this medication currently or has stopped long time ago ? This is important for use to consider possible side effects of the medication causing your conditions. As for viagra, it only helps to improve the blood flow to penis, solving the erectile dysfunction problem with no improvement on your libido.

Low libido can be due to psychological causes or biological causes.

• Common psychological causes can be stress, anxiety, depression, exhaustion and relationship problems. It is hard to identify and some people may even know they are having these problems.
• Biological causes can be due to changes in hormonal levels or some underlying health conditions. Changes in sex hormones in particular can makes you loss interest in sex as they helps in sexual arousal.
• There are health conditions such as diabetes, heart disease, hypothyroidism, cancer or surgical procedure that can affect a person’s libido.

There are a lot of causes that can contribute to your long term loss of libido. Your healthcare providers may need to ask more information, conduct a body check up and runs some test before determining the cause. As you mentioned the post-finasteride syndrome, the medication propecia/saw palmetto contains finasteride. It is a rather rare complications of taking finasteride medication. It can affect you sexually, physically, mentally and neurologically. These symptoms can linger on even after you stopped your medications. I would suggest you to seek help from healthcare providers, and mentioned the past medications that you have been taking.