The easiest and most important thing you need to do is go onto Play Store and download a "root checker" or "root verifier". Assuming you haven't rooted (jailbroken) your phone yourself, you can presumably tell if your significant other (or previous owner of the phone) has rooted your phone to gain access to all of your daily info. This would entail that your partner is computer-savvy, but there are other ways, too. If you bought the phone off ebay, the seller could have installed spyware on the phone as well (has happened before).
Other things to check are plain-sight tracking apps installed on your phone. Go into
Application Manager and delete any apps you don't recognize. Also go into
Settings > Security > Device Administrators and remove the rights from any apps you don't recognize (except for Android Device Manager). Most easy-to-use tracking apps will show up in that list.
Other than those two scenarios, there wouldn't be any way for a person to track you on the phone, unless they work for the CIA.
Hope this helps