DS is 5 months and EBF. From about 3 weeks he used to take a bottle of expressed BM once a day but that stopped on 20 August. Since then we have kept offering, tried different teats including tommy tippee and breastflow, tried various cups but he will have none of it.
DH, my mum, my aunt and two nannies (ours and a friend of hers) have tried. He has a few sucks but then explodes screaming and will refuse to suck, and the screaming lasts forever or until he crashes with exhaustion.
I have tried leaving him for a few hours, then longer periods, thinking when he is really hungry he will suck it up (literally). That hasn't worked - yesterday he had less than 4 ounces (I suspect closer to two) over a 14 hour period. I feel horribly guilty that I am starving him and don't want to jeopardise his growth - he was born six weeks early and has been gaining really well so far, starting on the 0.2% centile and now between 9th and 25th despite reflux.
I am absolutely desperate to get him to take bottles so I can go back to work. I work long hours and taking him with me is not an option. DH and I were also supposed to go on a one night trip in a country inn at the end of the month after what has been a really difficult year (horrible pregnancy issues, lost one twin, then my dad passed away and then several hospital stays with tiny preemie). We've already postponed it twice and I could really do with a break :( gosh I am wallowing in self pity aren't I? 
Please, please someone tell me how to get him to feed from a bottle! He used to take them with no fuss at all, which makes it even more frustrating.
TIA