Are my parents being fair?

I'm 17, and the eldest out of 3 (theres a massive age gap of about 8-12 years) and from a previous marriage, but I noticed my parents are quite hostile towards me. Just the other day, my grandparents came over and my mother openly insulted me (with no provocation) by saying I was "wet behind the ears like this person behind the counter" at some supermarket in front of my grandma. Just now, when she was ranting and raving about some insurance thing I asked what was wrong (trying to be helpful) and she just said "now you want to talk do you?" then completely ignored me. Sure I stay in my room a lot but I mainly do school work or read, because they just seem so hostile if I dare go downstairs. My boyfriend and friends think they're quite weird and hostile. Are they being fair? I try to be good, I try to find part time work and my hardest at school, but I don't get what their problem is...