Can a single NON-Married Jewish woman who is pregnant from her Jewish ex-boyfriend, get married to another Jewish man. I have heard that there is a mandatory waiting period for women who got divorced who had to wait some time before they were allowed to remarry, is this case similar or different since the woman was never married? Also, is the Sepharadic ruling here different than the Ashkenazi ruling? Please respond as soon as possible as this question is very critical in deciding whether to go ahead with a relationship or not. Thanks.
As you rightly note, there is a mandatory waiting period for women who are pregnant/shortly after birth until they can get married. This applies both to women who were married, and to women who became pregnant out of wedlock. Under extenuating circumstances, the waiting period after giving birth is shortened, but the rabbinate will usually not permit a marriage (to a man who is not the father of the child) during pregnancy.
However, there are unique exceptions to the rule that depend on personal circumstances, and I would therefore advise consultation with the local rabbinate, who will advise you on what can or can’t be done.
Sources: The reasons discussed in the Gemara (Yevamos 42) clearly apply to any pregnant woman, whether married or not. Shulchan Aruch (Even Ha’ezer 13) thus rules that the halachah applies even to a mezanah. Concerning the ruling of Rema, see Aruch Hashulchan 13:17, Bach Chadashos 58; Tzitz Eliezer 7:48; Emes Le’Yaakov 25.