I'm almost 34 weeks pregnant with my 5th kid. I have been getting back pain, head aches and loose stools. Are these signs of labor coming soon?

Maybe. Loose stools can cause contractions. The headache isn't likely related to labor. It could just be a headache, unless you have an elevated blood pressure. If the back pain is constant, its less likely labor. If every few minutes lasting 30-60 seconds its more likely contractions. The only way to know for sure is call your OB and see if they want you to get on a fetal monitor.