Was adding my ex bf on facebook a bad idea?

we broke up on the 1st of this month. he was ignoring me for months and would just meet for sex. he ignored me even when i missed periods because of the unprotected sex we had (but i took test and thank god i am not pregnant). i broke up with him because of this and it was a bad..bad fight. he said he was cheating on me, he has had sex with many girls before me and he going out of country he will have sex with many girls but denies it now and says he was just angry. i asked him if he didnt like me why didnt he breakup (because i could see he lost interest a long ag0 and was just pretending till now). he says though he didnt like some of my qualities but still liked being with me (which i dont believe because he twice said i am too boring..and he was getting bored with me..i mean i could see it) i feel he used me for sex...any way he asked for being friends and i agreed because i was too scared of losing him and him not being around. i cant ever possibly forgive him (right?) ..after the breakup when i agreed to stay friends i fought with him everyday..then he asked me out twice i said no..then i asked him he said he fractured his leg so cant come....then next few days we talked about what i was going to study and all..he asked if i got period then from 4 days we havent talked..i added him on fb sacred of losing him again (he is going out of country for higher studies so not possible to be in contact through phone)..but i am finding it very difficult being friends..i dont have the strength to see him any other girl ..i cant see when he flirts with girls on fb or girls flirt on him on fb..i think it should "unfriend" him on fb? because he will obvioulst add lots of girls..and i dont think i have the strength...i am also scared of the ay when he goes i will not be able to bear it....what should i do? i think i should just cut all contacts with him and focus on my studies..i have an exam next year for which i require some serious very studing...and he will be going in 2 months..i am scared he will tell me he is going i wouldnt be able to bear it and screw up my studies again ( i did this year also because i devoted so much of my time and energy at this relationship thinking it was going somewhere and hoping it would turn into something significant)