Im not sure what hes up too ?

basically me and my ex are getting back together when im 18 :) hes 22. im 18 in a couple of months, we decided 18 because i have my A level exams right now and i really need to focus on them :) thing is because of these exams i havent been able to talk to him much at all :( i havent been on facebook chat or msn for 2 months now, and tbh that was our main kinda contact when we werent together. i havent seen him in 5 weeks now :( it really really really sucks :/ we do text sometimes but not a lot. because of this lack of communication im seriously getting paranoid, i keep thinking how can you look forward to being with someone if A) you rarely ever get to talk to them or B) there is so many other options out there when your single like he technically is. On facebook he adds a LOT of random girls, sometimes they add him tbf, but he still adds some :/ i just keep thinking that maybe their an ego boost type thing, but i dont think so because he seems to talk to every single one of them, like he flirts with a lot of girls on facebook, saying stuff like ''then you'll have to buy me a drink xx'' hes also started putting '' <3 xxx'' on the end of paragraphs to these girls, and that used to be our ending :/ i know i sound so unbelieveably paranoid and clingy, but i really dont want to lose him :( it hurts that i could mean so little to him, for him not to post on my wall on fb or text me? :( iget that he could be busy and i have issue with that he has his own life to live and i totally respect that, but he seems to find time for these other girls :( hes so confusing i texted him 4 days ago, after liike a week of no contact, and he said he ''really missed me and was counting the days until he could see me <3 xxx'' it made me go all wam and fuzzy inside, but then we havent had any contact since apart from ''poking'' on facebook. I dont understand what hes up too. i dont think hed ever hurt me intentionally.. maybe because of so little contact between us, im just literally not on his mind, and those other girls are always on fb chat and msn probably so they can talk all the time? :( but if he missed me surely i would be? i dont know. what do you guys reckon? i care about him a lot and i usually wouldnt fight so hard for a relationship but he is so crazily perfect for me :)! he has said that i was perfect for him too, but why would he bother trying to find another girl? thats what it seems like with all this adding other girls and flirting pretty heavily with them? :( any ideas? sorry for the length and thank you for any responses :)!