Hi.... I appreciate your concern and your love for your boy friend. As the cause for the erectile dysfunction with your boy friend is diabetes it can be treated and also prevented. Talk to him and tell him it can be treated... All he needs to do is to follow his diabetic treatment in what ever form that is recommended to him strictly. Once his sugars are under control he will be able to overcome ED. Avoiding stress is equally important and tell him not to worry.. You can take the help of the sexologist if needed. One meeting with a doctor may help in boosting his confidence.. All the best..