Oh mama, I can imagine how worrying this must feel, especially as a first-time mum! From what I've heard from other mums with fibroids, that pressure and cramping sensation, especially after emptying your bladder, is actually quite commonly reported when fibroids are present, because they can press on surrounding areas and cause that uncomfortable tightening feeling. My neighbour went through something similar with a large fibroid during her pregnancy and she described it almost like a blood pressure cuff squeezing and releasing, which sounds very much like what you're experiencing. The honest truth though is that with fibroids as large as yours (over 8cm is no small thing), the experience really can vary quite a bit from person to person, some mums manage relatively well, but others do find the discomfort more intense as the uterus grows and competes for space. Please do flag this specifically to your OB or a maternal-foetal medicine specialist, because fibroids of that size during pregnancy really do deserve close monitoring, not just general reassurance.