I was so dizzy between 23-26 weeks the spinning head actually woke me up at night. I have always had low blood pressure, but this was nutz. The doctors checked but was no lower than normal (for me - 50/90). It seems to have eased now, (I'm 27 weeks) but one possible explanation was that i was busier than usual (moving house) or that i had recently stopped taking a medication (very low dose anti-depressants). During this time i also had severe stomach pain below my ribs all the way through my body. the pain was so bad a night i couldn't stand up to wash the dishes without crying. It went away too once the move was behind us and life calmed down to a slower pace. Have you perhaps been a bit stressed or busy lately?