Will the reason behind his lack of interest determine whether or not you stay with him? These issues can't be resolved overnight with a little blue pill. And it may be a secret you'd rather not want to know. If he feels as strongly as you that early on sex was "amazing," he should be RUNNING to get help. You may need to establish a deadline for him to get help and make it clear if he quits, you will too. Take care and good luck. Oh BTW, you know this is not your fault, right?