In response to your first note, the seme and uke only had sexual relations. They were not in a relationship beyond sex. Since the uke kept his feelings to himself, the seme did not know that the uke had feelings for him. Nor did he know that he too had feelings for the uke. It's why he failed to love the other people he's been with after the uke. All of his feelings came into the light after seeing the uke again.
Was he using him? In a way but it wasn't "intentional." The seme was oblivious. Let's just say that he didn't realize what he had until it was gone... better yet, he didn't realize until it reappeared.
So ch1 :why did they even break up ┑( ̄Д  ̄)┍? Was the seme just using the uke?
Ch3 :the only one that I actually liked (=・ω・=)
Ch4 :the one I hated the MOST (╯°Д °)╯╧╧
Ch5 :was ok . Kinda cute
Ch2-6 : hmmm :) ...