that's a tough call because you might be his "security blanket" after his recent break up. OR he might have feelings for you but he's just not sure right now because he just got out of a relationship not too long ago and might still have some leftover feelings for his ex that need to be sorted through in his head and brought to closure before he can truly answer that question for you. if it were me, i would just go with the flow, keeping in mind that it is an open relationship until "further notice". in a month or two (probably no longer than that) if you two are still "together" then ask him again how he feels about you and if you still get the same answer then it would be a wise idea for you to remain friends with him and move on. just my opinion on the subject:)