Why do I keep dreaming of my ex?!

Every night lately I have had different dreams but all containing my ex - and in those dreams we are either together (without explanation or hesitation due to have being broken up) or we are making out and have this connection while we are talking. Me and my ex broke up like 6 months ago and are on friendly terms, every now and then we talk vividly but I don't know what these dreams mean?! I don't think I'm necessarily 100% over him but I'm definitely not heartbroken and miserable over him!? 
Has any one else had this happen? What do the dreams mean?