No attraction to partner - affair?

my partner and i have been together for 6 years. we have a small 1 year old child together. we were a very loved up couple and i doted on him for years, he was my everything, my world. there was no greater person than him. in the last few months i feel like i have lost attraction to him and see him as a great friend rather than partner. we still have sex and plenty of it, its just not the same for me anymore. i am starting to feel like i am getting attracted to other people and i do not want to make the mistake of cheating. in all of the confusion i felt i packed up said i was moving out, after a few days apart he begged me to stay and said he would change how i felt towards him if i gave him a few months. so i agreed and felt good about it...until the last couple of days. we are only a week or two in and hes been trying so hard, there is no body else in the world that could love me like he does...and i feel like such an idiot. its just not the same anymore. i dont feel the same and i am so confused. its making me a mess...any one been through this before? suggestions? i am so scared of breaking his heart!