female lubrication

Hi. So I'm super embarrassed by this but in the past few months I've occasionally had trouble producing my own natural lubricant during sex. My SO says he doesn't mind but I do. I'm 21 and I've never had this problem. It's not always but it's often enough for me to wonder if there is something wrong? And is it common? Or if there is a way to fix the issue without using store bought lube?