I Understand where you are coming from but i honestly dont think you have anything to worry about. As you know your Immune system normally clears HPV out of your system within 2 years so if you have been unlucky enough to contract the virus it is more than likely that you do not have it anymore. You are obviously worrying a lot about this so if i were you i would have a smear just to rule it out and then you can stop worrying.
You will not be given treatment unless the cells are highly abnormal. if you just have slight changes to your cells they will leave them and you will have another smear 6 months later to see if the cells have gone back to normal. There are 3 stages of abnormalty of the cervical cells, if the cells are in the first stage of abnormality treatment will not be given because at this stage the cells normally go back to normal on there own but if the cells are highly abnormal this means that they are not very likely to go back to normal and may turn into cancer so if these cells are detected you will be given treatment to remove them.
Treatment for abnormal cells is a 10 minute procedure that happens in a clinic while you are awake. Having just 1 treatment very rarely causes problems with pregnancy, if you have more than one trteatment there is a risk of not being able to carry a baby to term because more of your cervix will have been removed and it will be more strain on your cervix but there are things that can be done during pregnancy to help. I have heard of a number of women who have had more than 1 treatment and have got on to have 2 or 3 babies with no problems.
You have nothing to lose by having a smear now privately it will put your mind at rest and you can still have your smear when you turn 25 on the NHS, you actually get the letter inviting your for your first smear 6 months before you turn 25.
I hope this helps Xxx