Hi and welcome Victor
To me that sounds like a collimation issue. Have a look through at this to get you started
http://www.iceinspace.com.au/63-390-0-0-1-0.html
Or even better yet, I see you're from Perth so there's a very good chance the scope was purchased from BTOW in Malaga. Pop down and see Keith and he'll show you how to collimate it for you. Also on Thursday nights they have open viewing so he can even give you a few lessons.
All the best!
Chris