Boyfriend having problems....

Amanda
My boyfriend of 2 1/2 years just told he is having issues getting a keeping an erection. He says he wants to have sex and is mentally there, but his body won't react. We used to have a very active sex life so this has been a huge adjustment and affecting our relationship. When we do have sex it is still amazing just not often enough. Anyone else gone through this? What can I do to help?