Your situation is very serious, and should not be minimized by anyone. You have great strength, and courage that is obvious because you have opened up about this before. Do not limit yourself your mom was in disbelieve. Regardless of what can be done legally, you need to let this out to your dad and get his support.
Also, you will want to get into some regular counseling to help you cope with this, and hopefully move past it. With your dad being aware, he can make sure you are getting all the help that you need.
Unfortunately, when abuse like this happens some people are blind to the fact that the perpetrator could actually do such a thing. It appears your mom is in a fog about this situation. Over time, hopefully she will come around and realize this is reality not a dream. This is your reality, and you need to not feel suppressed about it. There will be no easy way to talk to your dad about this, but it still has to be done. He is on your side.
Find a neutral time while you are there these two weeks, sit him down, and let him know what happened to you. Once you get it out, that will be a relief off your chest because it is not a secret you are keeping bottled up inside. After that, then you can pursue legal action, as well as individual therapy for yourself.
Stay strong! You are going to get through this, and the easiest way to do that is by speaking out and not letting it ever happen again. Reach for the inner strength that helped you talk about this before, and now use it to talk to your dad. You can do it! If we can help in anyway, but talking to you, your dad, your mom, or even helping make a report....please let us know. We are here for you 24/7.