At the beginning of my second trimester (12weeks - 3 months), despite not yet being visibly pregnant, I did start to feel the increasing size of the uterus, both from the inside and the outside. For about a month there was an occasional feeling of considerable pressure way down low, and I was a bit afraid that the little Mr. didn't know that he had another 6 months to incubate. My doctor said it was normal to feel the uterus so low down. It was small and gravity dictates that it stays relatively low. I fortunately figured out early on that I could move it up easily with a few modified bridge poses and I felt so much better. Instead of focusing on the backbending part of the bridge pose, I focused on straightening my lower back by engaging the lower core and lifting the tailbone up to flatten the small of the back then gently lifting the hips with the lower core engaged and the lower back flat, making the spine long and straight and the lower part of the pubis point up. Once my hips were lifted, I took a few deep belly inhales and exhales. Then lowered the hips starting with the top of the back getting the small of the back on the ground then gently lowering my tailbone until the (now smaller) natural curve of my lower back returned. A bonus for this pose is that it also happens to help with any swayback you might develop as your belly grows, and keeps your lower transverse and oblique abdominals in shape, which are oh so necessary and useful later in pregnancy and childbirth! Lifting the heels later (photo @ 6 months) helps to engage the thighs and keep the spine long. After 16 weeks, lying on your back for long periods isn't recommended, so I didn't stay in the pose for a long time, just long enough to move the uterus up a little. If my breathing was steady and long I did the pose a few times before coming back to seated position.
I also started feeling the little bump quite prominently from the outside. And by that I mean that when I was bringing my knee to my nose to place one foot between the hands from plank to prep for any standing pose, I kept feeling like I was mushing the little Mr. My simple remedy was to bring my knee to the outside of the same hand as knee, no longer squishing the lower belly, but still being able to gracefully (enough) transition from vinyasas to standing poses. Additionally, the moment I felt a bump in my belly, I no longer did any poses on my stomach to give the little Mr. all the space he needed.
Every person is uniquely different, and every pregnancy has its own challenges, so please ask your doctor before doing any new exercises. Mine told me to keep doing whatever I was doing, so I listened to my body and figured out how to keep doing my yoga. I hope you keep doing your thing and if you have any questions about my experiences, please don't hesitate to ask. It's an awesome journey!