My little peanut

I am 18 weeks pregnant I am 37 and this is my fourth baby have anyone experience over 35 and up that there is a lot of pressure to where sometimes you can walk from the house to the car or even be on your feet too long I know every pregnancy is different and I know I'm a little older but this last one hits different I could barely walk sometimes and the only thing that makes me feel much better is when I'm sitting down and I don't do till July if you experienced this can you tell me any kind of suggestions I can do that safe to take the pressure away