What Causes Yellowish Clear Mucus Running From Nose And Pressure On Teeth?

I have had yellowish and clear liquid running from my nose randomly 2 days this week. It will come on suddenly and sometimes when I bend over. I have had pressure on my teeth as well. Then the other day I thought it was just the yellowish liquid but it was watery blood. I still feel some pressure on my teeth and it feels like a sinus headache. The drainage and pressure is only on my left side. Do I need to see a doctor? Thank you.