21 weeks pregnant & feeling a lot of pain & pressure in my vagina. is that normal or should i go to the er?

Better safe than . .: Some amount of pelvic pressure is normal as the uterus grows and the baby weighs down on your pelvic floor. However, pain can be a warning sign of preterm labor, so it's better to be safe than sorry, check with your OB and go to the hospital that has obstetrical services. They will monitor you and probably measure your cervix.