Is insufficient rigidity / ED just a part of old age?

My erection seems to be not as strong as before, how can I know if I have insufficient rigidity / ED?

I have insufficient rigidity / ED because of low libido (low sex drive). Is there any suitable treatment for me?

What is the best treatment for insufficient rigidity / ED?

Should I try medicine treating insufficient rigidity / ED without a prescription?

Are there any other reliable and medically proven methods available if oral medications for insufficient rigidity / erectile dysfunction are ineffective for me?