Re: Pressure/Pain in buttocks???
It's probably some sciatica, which is caused be pressure to the sciatic nerve. The sciatic nerve starts about mid-butt cheek and runs down the outside of your leg down to your little toe on each side.
When I get sciatic pain (from a bad back) it usually starts as really tender-to-the-touch skin in my groin and inner thigh, then works it's way to the butt and leg and down the leg.
Another thing it could be is SI joint pain. The SI (sacroilliac) joint is a small bone that sits very near your spinal column, right about where your top pantyline would be if you had on a pair of bikini underwear. There is one on each side. It is carefully held in place by numerous ligaments and tendons
(and muscles), but that all gets shot to hell when we get pregnant because everything in the pelvis starts shifting around.
Anytime something is out of whack in your back/pelvic region the rest of your body overcompensates for it, which can cause undue stress on other parts of your back/pelvis. I can imagine that due to your increased weight and change in center of gravity that you are experiencing some problems like the ones I've described, and your other muscles and ligaments are trying to help out. When you move (as opposed to just standing there) they get some relief because of the movement, so they stop hurting.
You might ask your doctor for some stretches you can do to help you out... one I like is for the hip flexor. Stand next to your kitchen counter and hold on for support, then do a deep forward lunge. Make sure your hip on the side with the leg extended behind you is really opened up. You should feel a good stretch throughout your pelvis. Do that 5 times for a count of 10-15 on each side. I had to do that alot in physical therapy when I was recovering from back surgery and I still do it because it feels so good.