My shih tzu is making weird noises?

Me and my little cousin let my shih tzu outside to go to the bathroom this morning, and we left her outside for like 25 minutes while we were inside. we let her back inside, and about 15 minutes later we noticed that she started gagging and making weird noises in her stomach. Her stomach is like squeaking and turning. She is also farting a little bit. She is being really slow too, she usually runs around but she is just acting really laggy. What is wrong with her????