You can tell it through their actions; how they treat you or how they act when they're around. Everyone have that time when they won’t listen or talk to you as they are distracted by something.
But a person who cares will listen to you regularly, because your opinions matter to them; whatever that way is, they will listen. People who don’t care will not text you back. If you make no effort to see them or talk to them, you know, deep down, they won’t try.
When you’re talking, they will not want to know how you are doing. They won’t try to smooth things over if things go wrong. They will never consider your feelings, but instead think only of their own.
If you are doing the best you can with what you have, worrying if people like you or not is a waste of your most precious resource: your energy. Check out some tips on what to do when someone doesn’t like you at Psychologytoday.com.