I Have Small Whitehead Type Sores On My Lips That

I have small whitehead type sores on my lips that will open and ooze a clear fluid. This has occurred a couple of times a year for the past few years and never before that. I have also experienced an extremely large cold sore on the roof of my mouth recently. I am a female 66 years old and have been in a monogamous relationship for the last 10 years. Any thoughts about what may be causing this?