My X visa expires in 2 weeks.I need go my country,return back to university in 3 months.How to do?

I hold an X that will expire in 2 weeks. I must go to my country now for less than 3 months, but will return back to China and continue my studies.
-How to extend my X without letting it expire, knowing that the university will not do it for me as i will be abscent for 3 months?
-Do i need to apply for another X again after 3 months if my current one expires?
-Is there any other option?. Thank you.