Ouch! This sounds like a really painful situation.
Firstly, it can be worth checking into whether they really don't care... or whether we are making a bit of an assumption about why they're behaving as they do. (Often people's behaviour is driven by their own fears, worries, and hurts - and has nothing to do with us. But I know from personal experience that can be hard to understand on a feelings level)
Secondly, it's always worth remembering that other people's behaviour is beyond our control. All we can control is our own thoughts and behaviour.
Next, it can be very helpful to think about why what they're doing feels hurtful to us:
* does it remind of us an earlier situation, maybe something from when we were very young?
* are they touching on something about ourselves we secretly worry about?
* are we doing lots for others and getting very tired or drained?
* do we have expectations about how they should behave, based on our own preferences?
These can help us detangle a situation and see the wood for the trees. But at no point should we ever blame ourselves for other people's behaviour.
If we obtain actual evidence that someone genuinely doesn't care about us, it could be useful to do some reflection about why we keep them in our lives:
* deep down do we feel we deserve to be treated this way?
* are we worried what others might think of us?
* do we secretly like the 'drama'
and so on.
This might sound tough. Here's a thought: if we want to change a situation, we need to look at whether / how we are contributing to it... and how we can change our bit of the situation.
Some other people do care about us, but have never learned how to be respectful of our feelings and needs. It will be up to you to decide healthy boundaries for yourself:
* experiment with talking to them about how you feel about the situation. Use "I statements" (I.e. "I feel ______ when you __________" And use a real, specific example for that second blank). This works much better than saying something like "You always __________ and it makes me __________"
* you might want to consider whether or not to keep such people in your life, or how often to allow them in your life, and in what situations
If we decide to have this person in our lives going forward, then we'll benefit from setting some boundaries:
* what are all the things you could you try out, to limit the impact this person has on you?
* is there personal development work you could be doing to strengthen feeling good about yourself -- no matter what?
* what are some healthy ways you could express existing feelings of hurt, anger, frustration and so on?
I hope this helps, please do get in touch if you'd like to chat through your situation.