DS (8 weeks) has never had much of a problem with wind. Last week, however, he started to experience what looks like horribly painful trapped wind - very difficult to get out and the pain seems to persist after multiple farts and burps over several hours. In the last couple of days his poo has turned green and started smelling strongly of vinegar. There's obviously something going on, especially as it came on so suddenly, but does anyone have any idea what it could possibly be?