It sounds like you have been putting on a very strong front for a while to help support the people you love. As admirable as that is, it will be very hard to take care of anyone if you fail to take care of yourself... It can be damn scary but in most cases reaching out to your loved ones for help is the best thing to do. It may feel like you're failing them but you're not, you'll be letting them past your barricades. It takes a hell of a lot of bravery to do but could strengthen your relationships with them in the long run.
Here to listen if you need to talk some more