It sounds like it may be POTS - postural orthostatic tachcardia syndrome. Does your heart race when you stand up and are you dizzy ?
Whatever it is, you do need to see your physician.
Have you discussed this with your doc? I'm not to knowledgeable in the "expecting" area but "the high pulse/low bp" does ring a bell, but I'm not sure what. I've done a lot a research for my own issues and it seems as though I remember coming across that particular symptom but I don't remember what it meant. I'd post in the pregnancy forum to see if you can get a better response.
i was hit in te chest with air-bag in auto accident. i developed a racing pulse and swollen lower legs. it was heart failure caused by atrial flutter.