Wondering if anyone has had this problem and rectified.

Since changing my oil + filter when starting my car the oil ilght goes off then comes on for around 5 secs then goes off, I have changed the oil and filter twice 5-30 first and 5-40 second. I have also bought from Vauxhall the full black cap with filter attached + pressure switch still same may stop on slightly longer after second oil change, checked the pressure 50 psi idle up to 100 psi when reved. may be my imagination but the engine seems to be getting slightly noisier. could it be the filter that is draining back when left, this happens if left over 2 hrs. mileage 25000