Strange Back Pain - Middle of back??

Hi Everyone,

I am currently 5 months pregnant with my first baby and I have been experiencing some strange back pain. It all started at approx 3.5 months and I was 'sore' at the bottom of my ribs at the front which I just assumed was normal body expanding etc etc. Slowly it turned into the most annoying ache on the left side of my back only approximately half way up. I have spoken with the midwife and she said she has not heard of it but I have noticed some people complaining of it on various sites which i have googled. The problem is I dont know what it is or how to try and treat it. I have been to the physio and it has not helped.

My 'ache' comes on normally everyday after I have eaten at lunch and remains with me for the rest of the day. I am most affected when I am sitting in a chair and not when I am standing at all. We have the best ergonomic chairs at work so I have ruled that out and the same happens to me at home with a cheap chair.

I dont know what to do, its affecting me everyday and I hope someone can shed some light on it for me.

Thanks :wall: