Golfmechanic2795

Hey guys I'm new to this but I'm having a problem I'm struggling with. I'm an amateur mechanic and young so not a large amount of experience yet. I have a 2004 Silverado 1500 Z71 with a 5.3L motor and 230,000 miles. My oil pressure is idling at less than 20 lb on my gauge and will drop very quickly to almost nothing and light up "low oil pressure" and there's also what I believe is a lifter tick on my left side from the drivers view. I stopped driving it. My first thought was oil pump but before I get to that I'm in the process of flushing the motor because I hope it's just gunked. I've flushed it twice and so far still the same. I was thinking about dropping the oil pan and checking the screen before tearing into the oil pump. Any ideas?