Congrats on your second! I had "cramps" much of my second pregnancy, a lot like you describe. It bothered me somewhat enough to ask my midwife about it (there were days when I literally expected to go to the bathroom and have started a period!) but since I had no other pre-term labor issues/symptoms it was just something we monitored together.
I have two girls and my firstborn was a little lazybones in the womb and is most-definitely one of the most coordinated, active, and physically fit three-year-olds I know! My other daughter (born earlier this year) was a total gymnast in the womb and is still so! She's learned to roll, crawl, and sit up on her own on average 6 weeks earlier than her older sister's milestones. (the fine/gross motor skills are more toddler based, and gender is only one factor--I've seen many 6 month old baby boys with amazing abilities to grasp small objects and investigate threads on shirts, etc.!)
I had lots of dizzy spells with my second pregnancy but never worried about them. It was like you described, kind of a whooshing feeling, tingling my nerves or something. It was mostly when I changed positions. She also knocked me off my feet once or twice with her kicks, gave me a weak bladder during pregnancy, and broke my tailbone on her exit---
I would say as long as the feeling isn't constant, and you are able to rest well, it's probably what you think it is. I'd guess that the doctor might be suggesting the anxiety is coming from you noticing the feeling more than other women maybe?? That said, you should probably bring it up with your regular doc in the next visit. Did you tell this other doc that you know it's not "just anxiety?" Let your doc know you didn't feel "listened to" if that's the case.
Happy wishes for a fantastic 2010 and new baby boy!