24 week with placenta previa and a thinning cervix

at my 20 week ultra sound i was told i have placenta previa. its 2 cm away from my cervix, so the doctor ordered me pelvic rest, i am currently 24 weeks and started having contractions sunday morning so i went to the hospital and they set me up on a IV and after i finished the bag of fluids i started having more contractions so the doctor checked my cervix and it was thinner, i went to my doctors today and my cervix hasnt changed and ordered me bed rest. this is my first pregnancy and im so scared and have no clue what all of this means? does this mean im going to have me daughter soon? some one please help.