Can you be pregnat and than be pregnat again? having both child's 3 months apart, both babies bein premature

No: After the uterus is occupied with one embryo, hormones are generated that stop ovulation. Another conception will not be possible. There is a possibility of different sized twins within the uterus. Occasionally the dominant twin gains greater blood flow while the lesser twin is starved and can be lost.This can produce a situation where two different size babies are in the womb.