Sometimes we give so much when we have so little that eventually we find we've nothing else to give. Theres no shame in it and it doesn't make you a terrible person, in fact you should see it more as a reflection of just how much you've given and what a caring person you actually are. To be quite frank its about time someone did show you some support an love. Children with special needs do need more time and attention but its no excuse to neglect others. Try talking to your parents about how you feel and that even though you understand you'd like a little more support too. You are part of the family and by the sounds of it they are very lucky to have you. I'm glad you found somewhere you can share your feelings and feel accepted and supported. I hope things get better for you.