Every now and then when I try to talk to him abut something, he gets really angry at me and reminds me that we're not in a relationship, even if the night before we had gone out to dinner and a movie and had a wonderful time, and then spent the majority of the day cuddling or something. He goes from telling me he would marry me some day, and I'm his best friend and one of the best things that has ever happened to him, to telling me he's not serious about me anymore and we're not together and I should just accept that. I don't know what to do. When do I believe him, and if he wants to be left alone, should I respect that and leave him be, or still try to be supportive?