Lightroom Import Issue

I am having lightroomm tell me that i have previously imported files that I haven't. I am working with a high volume of photos on a daily basis and it hasn't ever done this even when the file numbers roll around. I don't have time to add another step of renaming files. Do I have a setting wrong? is there a fix? the metadata can't be th same, becuase it did it after I obliterated 38,000 files (that didn't have this issue til the end) and I don't have NEAR that number currently in my photos in LR. What can be done??