Bra for endo/adeno flare ups

[wejammin]

I'm currently going through investigations for endometriosis and/or adenomyosis (adeno shown up on ultrasound twice). I was diagnosed with IBS last year as most of my symptoms are digestive/bloating.
When I have a flare up (which is about 2 weeks each month) I'm bloated from ribs to pelvis.
I usually wear a 34E bra but go up to a 36 when bloated, but I'm still finding it so uncomfortable, like I can't breathe, which makes me feel panicky. I can't not wear one for work or sport. Does anyone have any recommendations for a supportive bra with a soft stretchy band that will allow for bloating/gas/whatever else this is.

M and S flexi fit.

@itsgettingweird thanks, I'll have a look at these

M&S sell bra extenders as well.

@WonderingWanda I've tried those but it's still too uncomfortable - I think it's the lack of flexibility in the bra round the front on my ribcage, rather than the back size on its own, that causes the problem