Flight deck, not cabin crew. Have experienced it mildly, not quite like you suggest, but over-the-counter mebeverine and peppermint oil worked wonders for me. Both are accepted by the CAA for controlling IBS.
Also, although it sounds obvious, manage your fatigue well - it may be a factor, especially as you say it has become worse since becoming cabin crew. When I went off sick for a week and a half, when it was at it worst, I realised afterwards how exhausted I was/had been. As the work slowed down a bit over winter, so did the symptoms.