I'm currently 27 weeks, and have felt great up until about a week ago when I stood up after sitting for a while and had sharp stabbing pelvic pains. The pain has continued for most of the last week as a dull pelvic pressure when sitting or standing with stabbing pains when I transition to walking. The pain is temporarily alleviated by yoga/stretching or lying on my side, and I can walk comfortably with minimal dull pain if I go straight from lying down to standing/ walking. I have had no abdominal pain or cramping.
The nurse at my doctor's office sent me to the hospital to be sure that it was not preterm labor. They verified that the baby is fine, I am not dilated, and am not having contractions. Their best advice at the hospital was that it may or may not go away before I give birth!!! I cannot imagine feeling like this for the next 13 weeks.
Up until last week I've been able to maintain my pre-pregnancy activity level with minor modifications. (Vinyasa yoga 2x/week and mile plus walks with our dog daily--just transitioning in the last 3 weeks to prenatal yoga) and would like to keep this up. But weekdays after sitting in the office for long periods (I try to move and walk as much as possible during the day) I feel pretty awful.
I am so sorry to hear that you are experiencing pelvic pain. However, I am happy to hear that you did seek medical attention and you are now having preterm labor.
It sounds like you are experiencing round ligament pain and maybe pubic symphysis.
The round ligaments are smooth, cord-like structures that attach to the top of the uterus and run downward, attaching again to the groin They are responsible for maintaining the anteversion (tipping forward) of the uterus. As the uterus grows they stretch and can cause sharp pain and discomfort. Round ligament pain is more commonly felt in the second trimester, but can occur anytime.
Because they attach deep in the base of the pelvis, they usually cause pain when changing positions quickly, especially moving from flexion to extension of the hips, moving from the horizontal plane (where they are not actively supporting the uterus) to the vertical plane (where they are suddenly called upon for support) and walking (where they have to support a constantly moving, jostling uterus).
There are some asanas that would be helpful. Those which bring the legs into flexion (squatting) or take the body into a more reclined position (supta baddakonasana). Generally, women who are affected by this are instructed to make slower transitions, allowing the ligaments to stretch more slowly and adjust more gradually to the added weight of the uterus.
As for the dull pain in your pelvis, it could be a separation of the pubis symphysis. (I actually just wrote a blog about this and ways to help the discomfort- Pelvic Pain During Pregnancy) Check out the blog for poses to do and avoid. You may also want to get a belly band that can lift some of the weight of your belly and alleviate the strain on your pelvis.
I hope these suggestions help and you find comfort in the rest of your pregnancy.