Lisa,
Noone appears to have mentioned the primary sharing site GEDmatch.com.
Upload your DNA file to GEDMatch, wait a day or so for it to fully process, run the one to many report and see who all you find who shares DNA with you there from wherever they've tested.
If you tested elsewhere than MyHeritage and FTDNA, you can also transfer into those sites currently for free, although FTDNA will charge a one-off $19US to unlock the tools and MyHeritage will begin charging new transfers for access to their DNA tools from 1 Dec.
If Ancestry to FTDNA it can be better to retest their FamilyFinder to fish in that pond for more matches as they are not as fully compatible as they once were.
http://genie.lornahen.com/lornas-links/dnalinks/atdna/#transfers
has some reading on that topic
PS your raw DNA is not visible to anyone other than the test taker (and anyone with admin rights on Ancestry or the kit / site log on elsewhere) only the secondary data of shared match lists..
It is also only a small percentage of your total DNA.