Question about prior relationship and property left behind.?

In an attempt at an online relationship, that became physical too early, didn't work out. Im currently trying to get my stuff back that i left, that they were going to send me. I orginally left them(online ex-gf and mother) a check for around 800. Not thinking about what my ex-gf said about previous loans from other people, that they would use it for their own purpose and swindle me out of my stuff and keep it and or sell it to gain more. I put a stop payment on that check, and "Tried" (with a capitol "T") to be civil about it and ask for the deminsions for the boxes that i would be sending. Thinking about that, i decided to give DHL a call and tell them about it and they said that i can't mail the check to them that i have to give it to when they pick up the packages. I am currently in the process of suing them for not cooperating and giving my stuff back. Its a sad sad situation, that i made. Please help me.