bending and stomach discomfort

I have recently posted about my 'spasms and breathlessness' but omitted to say that whenever I sit and bend over the desk or table I get an awful sudden feeling right below my sternum in the V under my rib cage, Its like a really bad hunger pang or baseball being suddenly stuffed up in there (I think it would feel like that) and it lasts for anything from seconds to a couple of hours. I have a hiatus hernia and big belly but this is a fairly recent development. I also react to certain food; this morning i had about three spoons of porridge with maple syrup and within a couple of minutes felt like i wanted to die because this sensation kicked in. Lasted about 15 minutes and calmed gradually. Could it be the hernia or an ulcer or what do you think? Have GERD too but this is a different severe sudden reaction.
All ideas appreciated. thanks