Wow I know exactly how you feel and like @Davictoes said I feel so guilty for not speaking to my family. In fact I beat myself up for not doing it and I guess that is what makes me so angry with myself.
Like you said I usually just nod, answer with a few words, or just shrug. My mind doesn't really go blank but I either think of what I want to say and then I just get so tired that I end up mumbling or I just get so angry and frustrated that I have to respond because I try so much to not be seen around the house. When I respond like this I call myself horrible names and go back to the cycle of negative thoughts about myself.