My stools are not pencil thin, but thinner than normal for me for last few days. should i worry?

Go to doctor: you have to to see your doctor and get a colonoscopy to rule out that there no problem like colon cancer.

Any other symptoms?: You haven't mentioned any other GI symptoms, so I am assuming that you are not noticing any pain or blood in stools. If the only symptom is slightly thinner stools, I wouldn't worry. Diet can affect stools. Be sure to eat a diet high in fiber and drink lots of water. See you physician if you notice blood in stools or have abdominal pain. Take care.