Problem solving help please!

Mollie
I tend to sit a lot at work. As in for most of the day. Then I go to school and sit a lot. I was combatting this by going to yoga in the morning and running in between work and school. Sadly running isn't real comfortable anymore and I can't take the heat at yoga lol so I'm a bit at loose ends. I haven't been able to find anything else that I can do safely before work. 
I've found that I start to hurt and feel real uncomfortable sitting all day. (Gas bubbles and back aching and tummy hurting and all the above. Only 9weeks so I'm not big yet). Any solutions you ladies use to minimize the discomfort?