A lot of pressure at 31weeks

This is baby #2. I’m 1 year pp. I’m having a lot of pressure in my down stairs area lol. It feels like she’s going to fall out every time I walk. They think she will be a large baby so idk if that has something to do with it. For my first I never had this feeling. It’s been like this for 3 days. Any advice on what’s going on?