That oil pressure light ON is a bad sign.
You've changed the oil twice, that's good, but more important is the service history, and what you're describing could be the evidence of poor maintenance.
It may be to late, but the only option is to get an oil pressure gauge on it and confirm where the normal operating pressure is at - a few things could cause low pressure, such as sludge, fouled oil pump suction strainer, bad bearings, .........