Ponylovingmomma, if the items aren't going to your old address, and if the post office doesn't take you seriously, or if you feel like they're not giving this situation their proper attention, you should go over their heads and file a report with the Postal Inspectors. They're basically the private police force of the USPS (they do detective work, carry firearms, and make arrests). They take this stuff VERY seriously, with it being a federal crime and all if your mail is being stolen. Here's the complaints page:
https://postalinspectors.uspis.gov/contactUs/filecomplaint.aspxDon't feel like you need to hold back anything. The more evidence they have, the better. It's just like reporting something to the police--they need as much evidence as possible. Be very specific, with dates, names of relevant persons, times, items, any past problems.