Distracted During Sex

Hello, I am new on this site, and just hoping to find some resources/help. My partner has ADD and we have what I feel is an excellent relationship - we communicate well and each try our best to cope with problems/issues as they arise. One issue I'm really having difficulty with is our sex life. Almost every time we have sex, he gets distracted, loses interest, gets it back again, repeats, and eventually gives up on reaching orgasm. He doesn't have any lack of interest in having sex, and we have a very loving and passionate relationship. The issue is just his inability to climax due to his mind wandering and then after a while he just gets frustrated and doesn't want to try anymore (and often a lot of time has passed from when we began, and we just simply can't go on anymore) I admit that sometimes I feel inadequate - that I can't hold his attention - but I also know that isn't the problem. I would love to hear if others have this same issue and how they have dealt with it, and if you have any solutions/suggestions of things we could try. Thanks!