Should I break up with my boyfriend of 6 years because I have a crush on someone?

It's even hard for me to write this but I don't have anyone to turn to. myself and my partner have been together for nearly 6 years and have been trying for a baby. he is the most amazing man to me, best man I have ever had the pleasure of loving and he treats me with such love and respect. I have never even looked at another man in our time together except the past 3 months which is worrying me. I am thirty and he is 26. I have not had the desire to have sex with him for some time, although I do suffer with pcos so I put it down to hormones. I have taken to having a crush gonna guy I work with (nothing to do with physical attraction) its more about his personality. I find that I am very sexually attracted to him. I have never cheated on anyone or even thought about it, and am completely against it. I am so worried that this means that I don't love my partner and I am just so confused. I need to make the right decision especially because we are supposed to be trying for a baby. I have had this same thing in the past where I randomly fall out of love with my partner but I really thought he was the one. any advice or similar stories? what should I do, I really want to be fair to him but can't face breaking his heart and ending our relationship.