No af since Jan 18th, no pos preg test...

So, I have a 5 1/2 month old son. They are now telling me I have high grade cells on my cervix again, and if I have to have surgery again it'll mean a hysterectomy for me at the age of 25! I've taken a few pregnancy tests, but no positive ones and haven't had af since Jan 18th. I have hypothyroidism, and I know that my periods can be irregular, but I'm at a loss for what to think.