I Dont Understand Why Im Feeling This Way

For almost 3 years I invest so much love for Him. I can't even go on a day without talking to Him. Hearing his voice gives sparks on me. I miss Him everyday even I talked to him. I love Him so much even He is so hard to love. But why everything has changed now. I've changed. My feelings have changed. Maybe because I'm just tired, tired of showing love, care and all but he never sees it, He never even appreciate my effort. He break my heart many times. Now, I can't feel the spark anymore. Every time He says He loves me my heart aching. when He says He miss me my heart aching. i just don't want to hurt him I don't want him to feel that I've changed that I am not happy anymore. It's just so hard to decide whether to walk away or try harder or just go with the flow where it will lead us.