Talk to Sexologist on Erectile Disfunction

I received treatment for hand tremors for a long time and used medication for about a year. After that for quite a while now I have not been feeling proper hard erection in my penis. Even if it happens it lasts for a very short time and full hardness is not achieved. Initially I thought it was a temporary problem but now it has become a matter of concern. Which type of doctor can provide the best treatment for this