Hi. I am 25 weeks pregnant with twins and I am feeling a lot of preasure in my rectum and some in my pelvis. What does this mean? Should I be alarmed?

I had the same toward the end of my [singleton] pregnancy. 25 weeks is where the babies really start growing fast, it may just be your body adjusting to all the added mass/weight of the babies or yes, it may signify something more serious. Best to contact your ob/gyn and at least ask. If it's painful or comes on very suddenly then I would advise to definitely contact your doctor.