I'm sorry you find yourself in this predicament.
If it's an option for you, you might consider abortion. If not, they might opt to do a lletz even during pregnancy, but you should definitely ask your doctor about that. Is the CIN3 of the squamous cells (on the surface of the cervix) or is it in the cervical canal? The former would require cutting less and would preserve your cervix more. I'm not sure how much the anesthesia and the procedure could affect the pregnancy.
Yours is a very difficult decision. If the idea of having another child gives you absolutely no happiness and only worries and stress, it might be best to terminate the pregnancy - if that is morally and emotionally acceptable for you. If not, things have a way of working themselves out and I'm sure if you decide to have the baby, things will turn out fine.
(((hugs)))