Hi Shanda:
don't let your doctor rip you apart. He's only sizing you up compared to a weight gain chart, he's not looking at you as an individual. This happened to me during my fist pregnancy and it was very upsetting, I ended up leaving that OB GYN office and writing them a letter to tell them that I was not some naughty school girl to be treated with the rod, but a person growing a baby who needed nurturing. Of course, I got no reply!!!!
Your body weight gain will follow a pattern specific to your body and this pregnancy, and he should know that. Ignore him and follow your own instincts: if hungry, eat. If not, stay away from the hamburgers!
I did step aerobics up to about month 4, I hadn't discovered Cathe then so I was using Charlene Pricket and did OK, but as I noticed that I was lacking energy to do fly over the top moves, I switched to swimming every day for a mile which kept me in great shape, helped keep stomach muscles toned and also made me feel light and sleek whilst in the water! So good for the soul.
After about month 7, I went back to the UK where I had no access to a good pool so I walked every day for at least an hour and that was great too. I didn't do it for fitness, checking heart rates and all, just to keep moving and get rid of lega and back ache.
So, you can see, that your body will respond differently from one week/month to the next, and you will need to reduce intensity continually, but you do not have to reduce yourself to bed rest either. I disregarded any doctor's recommendations to not raise heart rate beyond a certain level, because I was already in good shape, so Iistened to my body and took my cue.
The weight gain thing sorted itself out just fine, some months a lot, other months none or little: in both pregnancies this was the pattern, result, 2 very healthy babies who are now strapping girls!!
One caveat: Interval max should probably be avoided. Interval training is not recommended for pregnant women, you don't want to reduce the oxygen getting to the baby. But there's no reason to give up on weight training!
Good luck to you and remember to trust your inner voice
Clare