I'm so sorry you are going through this.
I used to have the same problem.. (still do at times). What I found really helpful is remembering that you are not responsible for feeling anyone's pain. Everyone is responsible for their own emotions and taking it on doesn't serve you nor that person. I find being aware of what you are experiencing at the very moment very helpful. You can ask yourself a question whether the stuff you are feeling is yours or someone else's, and if you aren't sure you can simply ask yourself "What reason do I have to feel this way?". Sometimes being simply aware that the emotions and energies you are experiencing aren't yours is all it takes for you to be able to simply tune them out (they just leave) and not take over you and overwhelm you. I feel that protecting yourself and trying to block everything out only exhausts us even more. I highly recommend the book"Self-Care for the Self-Aware: A Guide for Highly Sensitive People, Empaths, Intuitives, and Healers" by Dave Markowitz. I found very helpful guidelines on how to handle my empathic abilities there. I totally understand what you are going through, what you are describing is something I was experiencing for a long time. Don't lose hope there are ways to cope with this and remember you are not in this alone! I hope this helps. I wish you the best.