Bipolar Meds loss of libido

My boyfriend was just recently diagnosed with Bipolar Disorder, after a manic episode, and was prescribed 2mg of Risperdal and 600mg Depakote (both twice a day)... It is really working for him, he is very stable and rational on the medication, but I noticed while he is on it he has a dramatic loss of sex drive, almost none, and it is hard for him to get an erection... this is a big change because he was very easily stimulated with me before... Is this short term? The medication is working so well for him in all other aspects of his life, but I just feel so terrible, undesirable, and unattractive even though he constantly reminds me how much I am, and that he loves me so much... I realize that it is his medication and do remind myself, but I still can't stop feeling bad and I am constantly crying about it... I just don't know what to do because I love him so much... Do you have any suggestions? Should he tell his doctor? Are there any other medications that don't cause a loss of libido? It's hard to think about changing his medication though because this one is working so well for him... Please help. Thanks!