Is it true if you don't ovulation you can't get prengant?

Yes: Ovulation is the process of releasing an egg (usually only 1 from one of the ovaries per month). If no ovum was released, there can't be fertilization --> no pregnancy.

Yes: Without ovulation pregnancy cannot happen. Ovulation refers to egg release from the ovary. Once the egg is released, sperm can then fertilize the egg and if this is successful then a pregnancy happens.