Oh dear, you are not alone in this, quite a few mums have shared that around 24 weeks, when the bump sits low, walking can feel almost debilitating, like the pressure is just too much to bear properly. From what I have heard, when baby's position is very low, it can cause that uncomfortable, heavy feeling right in the pelvic area that makes each step quite painful. A friend of mine actually went through this and she said the best thing she could do was simply rest as much as possible and not push herself to keep moving when the pain was bad. Some mums also find that wearing a maternity support belt helps to take some of that pressure off while walking. It is really worth mentioning this to your doctor or O&G specialist though, just to rule out anything like SPD (symphysis pubis dysfunction) and get proper guidance for your situation, wishing you a comfortable pregnancy ahead, dear!