my sexual attraction has turned from a basic instinct to an optional one

Hello. I hope you will help me here with advice because in recent years my sexual attraction has turned from a basic instinct to an optional one. No, don’t think, I continue to have sex with my beloved, the father of my four children, whom I have been married for many years. Sex is nice, but we have only to dreamily remember crazy passions. We do not have the passion between us that was at the beginning of our relationship. Tell me, on the Internet, there is that women came up with Viagra. Does it really increase sexual desire?