I'm Currently Pregnant With Twins And I'm Only 23 Weeks

i'm currently pregnant with twins and i'm only 23 weeks but my belly has dropped a lot in the past day or two and when i walk or even sit i have excruciating back pain and cramping in my pelvis and groin area i have tried heat and it only helps for a minute or two but then the pain is back on a scale of 1-10 its almost reaching a 9 and the cold simply makes it worse and i'm freaking out because I've carried before but the pains are completely different from my experience with my previous pregnancies