Cervical dysplasia terminology can be very confusing and I am sorry that you were not better informed by your physician.
CIN 3 is classified as severe dysplasia of the cervical cells. Adenocarcinoma in Situ (AIS) is a sub category of Atypical Glandular Cells. This means that in addition to having cervical dysplasia, rated as CIN 3, you also have atypical glandular cells on your cervix, rated as AIS.
The CIN 3 is not cancer but could lead to cancer if not treated and may recur after treatment. The AIS is considered cancerous.
The follow-up for both of these conditions is a LEEP procedure, which you have had already. After that you need to repeat a pap in 4-6 months.
Here are some things that contribute to cervical dysplasia and cervical cancer, changing lifestyle habits could help prevent recurrence:
Oral contraceptive pills
Intercourse before age 16
Multiple sexual partners
Unprotected sex and condom use
I hope this information helps, good luck and keep us posted