How do i be honest with him?

okay so i started talking to this guy, now we text and stuff, we went on a date last week, and my friend is friends with him and talks to him and she knows he likes me. he has also told me that he likes me and he wants to go on another date, just i dont think i can. i dont like him and i dont want to hurt his feelings. hes really nice just i cant seem to like him like he likes me. plus, i have an ex and weve been starting to get closer and closer and i want to focus more on that. when i first started talking to this guy who likes me, my intentions werent to go out with him, but i think thats what his intentions were. i need to tell him somehow so he doesnt waste his time on me, just i really dont know how to because ive never been in this kind of situation before. thanks!