Dreams about kissing and being with an ex?

Okay so I have a bf, let's call him Joe. Joes wonderful and my feelings for him are extremely strong. And I have an ex named bob. Bob was nice to me, but ended up being a HUGE jerk! It only lasted 2 weeks, but I fell REALLY hard. Lately i'v been dreaming of bob SO MUCH though. I'll have dreams where it replays the fight we had or I'll just have dreams with him RANDOMLY in them!! And i'v only dreampt of Joe like 2 times. Well I just had a dream that I was THINKING about kissing bob. Where in the dream I knew it was wrong because Joe is my bf, but that I wanted to do it anyway because it felt so right. And then it transpired where I was in my old 7th grade clroom (I am in high school now) and bob was in my homeroom and we were sitting by each other. And IN THE DREAM, I felt the feelings I used to feel when I liked bob. What does this mean??