HELP please!!

Ok 29 wks and 5 days this is baby number three so I should know these things however this pregnancy is different.. Thursday I found myself in labor and delivery I was light headed and cramping, like menstrual cramps not contractions.. my bp was 75/43 they said that it was really low... normally I'm 105-110/50-60. .. what would cause this and what are my risks??? How can I raise it?? They finally let me go after 6 hours fluids and my bp was up to 99/45... I do have a doctors apt on wed but I am worried... any insite???