Possible oil pump problem????

I have a 97 Lumina 3.1 w/ 130000 miles and this morning when i started it i heard knocking for about 1-2 seconds and went away. It did not come back for the rest of the day. I check the oil it is full. I notice that the engine seams to be running a little rougher than usuall. Any seggustions on the problem. Thanks.

Shawn