Low oil warning but oil is full

[GoldmistXL]

I have been getting alerts on the dashboard that the oil level is low, and to add oil. This happens mostly when I first start it but also happens occasionally when driving. I have checked the oil level several times and it is full. I have also noticed that the oil pressure is low (@20 psi) when at idle but bumps up to normal (@40-50 psi) when driving normally. I never noticed that occurring before: It always used to be @40+psi. Why am I getting this alarm? Why is the pressure gauge fluctuating that much? Could something be clogged? Any help would be greatly appreciated. Thanks!