Older boyfriend and now lack of ?

My boyfriend is 18 years older then I am. He's in his early 40's. Anyways, we have an amazing relationship of almost 2 years. The is lacking in the last year. It's partly because of his anti depressent medications. He was severly heart broken from his previous relationship before me. Now that the honey moon phase of the relationship is over. He's satisfied with once a week and i want it everyday im in my 20's! Is this loss of libedo also something to do with his age? What is a girl to do?