Can my location be tracked/can my phone be duplicated I believe someone is keeping track of me via my phone. Is this possible and, if so, what can I do to disable that? Also, is it possible for someone who has had access to my phone to duplicate it so that they can see my texts?
As soon as there is no details in your question I'll answer in general: if you've got an android device - you could be tracked. This is not only about some sort of embedded Google telemetry or hidden spying apk - any app, that has permission to access your sms/camera/other data can do so.

This is how it may look like:

:

Of course there are couple of ways to avoid such a mess


Download and install XPrivacy. It's free application and it's rather hard to use, but this is the most clean way as soon as this app is opensource. Further instructionshere. Root access required.
Use other restricting permission app: there are plenty and here is the quick comparsion. Check out this and this tool. May require root access.
Freeze suspected apps which receives sms. This tool could do the trick. Root access required.
Just do not install any app that desires sms privilege - kinda tricky but the only way if previous are not possible.