(((((((((((( Rachel ))))))))))))))))

I am so sorry for your loss and for what you are going through now. Do you have anybody that you can talk to about this? A school counselor may be helpful or may be you can ask your family if you could see a therapist. It sounds like you have a lot feelings that you need to process.
Your dad would not want you to feel bad about this, as you said he wanted you to know how much he cared but you wasn't ready for that and that's okay.
The grieving process is a hard one but make sure that you allow yourself to experience that even if your family doesn't seem to be feeling it remember grieving is different for everybody.