Dear Maddgranny, Some of the chemotherapy medications used to treat breast cancer can affect the ability to get pregnant by affecting hormone levels and leading to menopause or the stopping of the menstrual cycle. This can be temporary or permanent depending on the age of a person and how close they were to natural menopause. You may want to discuss this issue with your doctor as to the likelihood of resumption of periods (thus ability to become pregnant) in your individual situation.
Yes, in some cases, a woman can get pregnant after chemo. Sometimes, though, chemo will destroy the ovaries and then that ends any future pregnancies. Also to consider is the ER/PR status of the cancer. If you are ER/PR positive and they put you on Tamoxifen, you should not even try to get pregnant.
However, your question indicates that a menstrual cycle is not happening. In that case, no a pregnancy cannot be achieved. No menstrual cycle means no ovulation occuring. That doesn't mean you cycles won't return, they might. If you want to have a child after chemo, I would suggest discussing this with a Reproductive Endocrinologist who can guide you in your options.
There is also a website with many stories of women who go on to achieve pregnancies and have healthy babies after chemo : pregnantwithcancer.org