I was having the same problem (I'm 45, too). 10 days ago I started taking Leopin 5. that's the japanese name. It's marketed in the U.s. under a different name. It's Korean ginseng and aged garlic axtract. I noticed a bit of a rise (no pun intended but it's appropriate) in my erections. Just a few days ago I started taking Maca and oh mygod, there is no doubt--my erections are much better and ejaculating easier. I ordered from this company: http://www.peruvian-maca.com/
good luck. At the same time I started taking St. John's Wort, a B1 and 12, E, c and an amino acid mix.