Thank you for posting. It sounds like things aren't going well for you at the moment.
Is there another older family member you could speak to? Someone who you could talk to that could then approach your dad and step mum with you and try to work things out.
You don't say how old you are but you mention working late, so I'm wondering if instead of being in your room while others get dinner ready, is there any way that you could help getting dinner ready? Even setting the table could be seen as helping and that way you would know when dinner was ready.
It's hard I know but sometimes when we feel excluded it can be that we are excluding ourselves by our own actions. Parents sometimes see this as us being rude or wanting to be alone. Maybe your parents think you want to be alone.
It's sad if your step mum speaks to you that way which is why I think it is important for you to find someone older that you can talk to. Someone you trust who could help you work out your next step.
You have taken a big step by posting here and you should be proud. It is safe here and you can talk freely about problems you are having. The people in here care and are here to try and help.
Hope to chat again soon, if you feel up to it.
Sorry to read you are having family issues. It certainly is not acceptable for your step Mum to talk to you like that. Can you talk to you Dad about how you are feeling?
Sadmushroom has offered some great advice, hopefully you will consider what she has said.
One of my nieces came to me with some issues, I was then able to talk to her Mum about some of the stuff on her behalf and things were sorted out.
If you feel comfortable doing so, you could phone up the helpline here at Beyondblue and the support people may be able to suggest help you can receive in your area as well has sharing how you are feeling here.
You seem to have a good relationship with your sister, if you are in your room, could your sister come and get you? It is important to eat, so hope you manage to find a way to make it to meal times or ask what food you can have from the fridge or the cupboards.
Please let us know how you are getting on. Hope some of our ideas help.
Cheers from Dools