Sorry you are having a rough go of it right now. Having been a preceptor for many "new" staff/students/etc. my advice is to speak up. As you said they don't know what you've done from one day to the next so let them know. Also, ask them if you can do things if they "stick you on a chair in a corner." If that doesn't work and you're still brushed off then try to WOW them by studying up, ask questions, and most of all let them know that you are truely interested in what they/the team is doing. What usually burns everyone out is teaching people that just come and go or are just there to get their hours in and then are never to be seen again.
Good luck and I hope things turn around. You'll find strong personalities in any OR you visit.........find the ones you like to work with and then do whatever you can to stick with them and let them know they are appreciated