I'm having some family problems? Please help!?

So lately I've realized that my father is on the computer a lot. and I mean a lot a lot! He's always too busy for us, too tired, and never spends time with my family. I'm a student and with my homework piling up I really need my laptop around to do homework and I constantly see him using it for important things. Either he takes it to his room, or to the bathroom. As if he is doing something soo important. Recently I've caught him going on random chatting websites that I've never heard of and then he stays there for hours until the battery dies and I know its something stupid because I keep getting notifications on my computer saying that I should watch out cause I'm close to getting a virus. Im sure its not cause of me because I don't use it unless its for schoolwork. My sister has talked to him asking him to stop and he did for a while but now he continued and ive realized his attention is all about that now. What should I do? I don't want this to end in the wrong way? and im his daughter.. i cant punish him or anything and i dont want my mom to find out and get hurt. Im so confused. i dont know what to do and im so scared. should i be worried?