My age is posted, i'm 18...why?
I would say that this is definitely something that you need to address. It is completely understandable that you having feelings of guilt not only about being abused but also about being the abuser. The good thing is that you now realize what you have done is wrong and you are not sounding like you'd do it again. It is not uncommon that a child who is abused becomes an abuser, but it's good to see that you've stopped the cycle in its tracks. I would encourage you to seek counseling to deal with the feelings associated with this kind of trauma; together with the councilor you might find new ways of dealing with your feelings. Counseling is really accessible, you can find it at your school or ask about free counseling at a local clinic...you may not like the first councilor that you meet, but don't give up...sometimes it takes a little while before you find one you can really connect with.
hope this helps.