Hello DH23,
I am so sorry you are getting such poor advice. I would gather a second even third opinion. As someone who has always been active, I find it appalling and nonsensical that any medical doctor would dispense with such old-wives folkish advice.
Unless you are deemed high-risk (yes I know given your *age* your doctor may deem you high risk) such as having an incompetent cervix or have an increased risk of miscarriage (if you have had miscarriages before), then YOU should be exercising.
I am now in my 2nd trimester and have gotten the opinions of 3 doctors. 2 out of 3 gave me the okay to continue working out. Granted nothing overly strenuous such as starting a marathon.
The less you move and the less active you are the more bloated, fatigued and disgusting you will feel. The advice I have also received from women who have been there done that (such as my helper, my masseuse and friends who have all had kids, granted yes I understand they are not medical experts) is that YOU should move and exercise. It will help you when the onset of labor starts and help make your labor a smooth one.
IN my first trimester, I got turned away by a lot of places in Hong Kong, including the Pilates studio I frequented. It is in my humble opinion that Chinese and Hong Kong-ers are extremely conservative, perhaps to an uneducated fault when it comes to pregnancy. You are pregnant, not disabled. Exercise does not bring on miscarriage as relayed to me by my close friend, a PharmD, and by a relative, who is a practicing medical doctor in the U.S.
If in doubt, you can always reference
What To Expect When You're Expecting, Pregnancy, Baby, Babies, Toddler, Parenting -- WhatToExpect.com
I have a copy of the book but sometimes still use the online web site as a reference. In the meantime, get moving but just don't start any marathons or go sky-diving.
Best of luck!