honest opinion:
he never added you to facebook before now - he's keeping tabs on what you're up to since he quit the relationship....from my experience it's classic behaviour of the push me-pull me type of bloke...sorry if you think this isn't the case, but perhaps you're not as impartial about this situation (too close) as is necessary to realise this
From experience this type of guy or indeed girl "Doesn't want you, Doesn't want anyone else to have you" They dangle themselves intermittently like a carrot on the end of a piece of string always staying slightly aloof and out of reach emotionally...
2 things - him knowing your every move sucks....he didn't want you...why should he know what you're up to...if he wants that...he KNOWS what to do...keep your life separate, if he wants insider knowledge that's his own look out....
and secondly, OMG sweetheart I've been there with access to my exes fb after a break up and it (pardon my french) f*cks with your head BIG TIME....every time they add a friend, make a comment...they're drawing you back into the flame and burning you each and every time....
for instance how are you gonna feel if he starts adding women you don't know? You don't need to see that, it would just be him rubbing your nose in it
there's another reason why I hate social media
disclaimer: I'm under the influence of several meds, out of my head with viruses and been burnt by relationships too many times then I'd like to remember...and seen my fair share of emotional vampires
....take my advice with a grain of salt - I mean well and have no intent to cause offence, but can't stand to see people hung out to dry, held on the end of a fishing hook etc etc
If any of this helps I'm glad and if it doesn't I'm sorry and I'll shut up in future xxx