Mucus discharge

I went to my doctor today at 34 weeks and I explained I have found lots of mucus discharge for the past week. One time covering my entire panty liner! (Sorry gross Ik). I've also been having cramping at sporadic times. He tested me for infection because he saw lots of yellow mucus. All tests came back negative but he did say it could be caused by contractions and to call if I felt any cramping at all. He didn't seem too concerned but should I be? Anyone else have a simalar experience?