Weird pressure?

So I’m 35w5d with baby #3, and I keep getting this weird pressure any time I’m standing that makes me feel like I’m going to pass out. It’s like a pressure low in my pelvis, and if I stand for longer than a few minutes, I start to feel light headed and dizzy. It’s been happening for a few weeks now, but it’s really bad today. I need to sit down more often than I should. Anyone else experiencing this? I have a doctor appointment in a few hours, I’ll ask about it, but just wanna see if I’m just a weirdo. Lol