The worst back pain ever!!

Hello ladies, yesterday was my other halves birthday and to celebrate we took a trip to London. We had tickets for Walker Stalker convention, which was awesome, then tickets to see Agatha Christies Mousetrap in the West End. 
After a long day walking at the convention and getting around London using the underground etc, by the time I sat down ready for the show my back was absolutely killing me and my tummy was also so tight and it felt like baby was trying to pull his way out using the umbilical cord! I could not get comfy in the theatre and must have looked a strange sight wriggling in my chair trying to find a bit of comfort! 
I'm 22 weeks and this is my 2nd pregnancy. I don't remember ever being so uncomfortable first time round but it was 8 years ago, I'm 30 now and I definitely think my body just isn't as tough as it was back then!!