Oil light turns on when driving slow (under 20mph), idle, when stopped. Turns off when driving.

2000 Mazda mvp.

Bought about 6 weeks ago, knew it had slight oil leak when I got it. Oil light stayed off.

Today got:

• oil change
• power steering fluid change

Now the check oil light turns on when I'm either driving slow (about under 20mph), idle at a light, or stopped (with the engine running).

Looking at google I found theories like:

• oil pressure sensor might have an intermittent connection problem due to corrosion.
• really worn engine or oilpump

Just wondering if anybody else has encountered this problem and did it appear after an oil change?