Why can't I stop dreaming about her?

It sucks, it was a short term relationship and she ended it, its been 6 weeks and I still have feelings for her, although it isn't really as painful as it was originally. I liked her for like 6 months prior and we dated for 2 months, she ended it because I was too "clingy' and I was her first boyfriend. Few weeks ago I would dream that we were back together and wake up and feel like sh*t, but it would fade shortly. More recently I've been dreaming about her, but not in a romantic setting, just as friends, like hanging around her with mutual friends, talking to her 1 on 1 just as a friend and such. I wake up and feel even worse than before, since we were really close for 3 months and its been 6 weeks and she hasn't contacted me at all, so it's like I don't exist anymore. We still hang out in a group once a week and it does make it harder, but I want to see my other friends too. Why do I keep dreaming about her, why can't I get over her already!
Why can't I stop dreaming about her?
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