Cervical abnormalities and cervical cancer are caused by certain strains of the HPV virus. This is a sexually transmitted virus which basically everyone who is sexually active gets at some point, but most people naturally clear it and build up an immunity without ever knowing they've had it. Some women - for reasons medical science is not yet clear about - cannot generate enough of an immune response to clear the virus, so it becomes peristent in the body and after many many years can (but doesn't always) cause abnormalities which then sometimes (but not always) go on to turn into cancer.
I am not a doctor, but this very specific cause of cervical cancer suggests to me that any cervical abnormalities that you may have would be completely unrelated to the leukaemia you suffered as a child. It's difficult because so much is still unknown about the causes of leukaemia, but as I say, because cervical cancer has such a specific cause, I can't really see how the two things could be linked, especially as the HPV virus is sexually transmitted (so therefore you will have got it years after your leukaemia) and is a local virus (meaning it is confined to the cervix and cannot 'travel').
The other thing to bear in mind is that while cervical cancer is rare these days, cervical abnormalities are relatively common and in the vast majority of cases, easily and successfully treated without too much trouble.
I know it's impossible not to worry, and I cannot imagine what it must be like for you to have had a childhood cancer and for that to be lurking in the background for you when something like this comes up, but it sounds to me like it is two separate things that are not related. As I say, I am not a doctor or a scientist, but given what we know about both kinds of cancer, I cannot see how having had leukaemia would increase your risk of cc.
Take care and good luck with your colposcopy.