This is time to get a quick check by the MD. Many things can cause the problem and some can have some rather unpleasant consequences. Though manual manipulation techniques may help somewhere down the road, they won't cure a medical condition that could be causing the problem. Blood glucose, cholesterol, falling testosterone, raised estiadol and prolactin levels as we age can all contribute. Make certain that nothing more serious is going on and then look into the fixes. Personally have had this for years and I would state after having tried numerous more common fixes that the only one that was nearly 100% reliable and really made things fun were intracavernosal injections. If the MD says you have been greeted with the ED monster, forget the orals. They simply are not consistently reliable. Sometimes they work, other times they fail and you've downed a very expensive pill for nothing. . .
Been there myself, and the best of luck to you my friend.