In our National Constitution & Bylaws this is addressed. If you don't have a copy of this you can go to the national website and under support go to resourses. You will need your initiating chapter name and you member id number to get in as this is a members only portion of the site.
Go to: Bylaws, Article 1 Membership, Sectoin 3, Status of Initiated Members, Clause 1 Activie Collegiate Status. I think D is relevant to your situation.
It basically says that unless you have been gone from your chapter for two or more consecutive academic terms, excluding summer school, you have to go back. If it has been two or more consecutive academic terms then you do not have to go back. If you want to go back after this time period, you would have to do so by written notification to the chapter.
So if you are not registered at school where you were initiated for two consecutive terms (excluding summer school), then you don't have to do anything. If you were gone only say the spring semester then came back the next fall, you MUST go back to the chapter.
I can't tell from you post how long you have been gone from your chapter. If you have any other questions, please PM me.