Walks while pregnant

So my mom went on vacation the other day and asked my to dog sit. I really love dogs and my daughter could use a little friend till baby gets here....soooo of course I said YES! ☺️ I took her for a 15 min. (Roughly) walk and I was getting right side ligament pain (more like discomfort) I know it's normal to feel this since your bump is getting bigger but I didn't feel it till I stated walking. Anyone else try to stay active during their pregnancy and feel this? Or during exercise? Walking the dog? Etc.?