how does it feel when you're about to orgasm

so I never have before, but sometimes when my boyfriend has his hands down there or is going at it with his tongue (I've never had like baby making sex before) I get this feeling like I'm about to pee? 😂 like my legs will start shaking and I feel like I'm going to pull his hair out, he usually stops because I get loud, but yea. is this feeling like I have to pee normal? I assume that I don't have to pee every single time I do this, especially if I go to the bathroom before hand, this is just what it's supposed to feel like, but it causes me to try really hard to hold it in (which I don't even know if it's possible to hold it in)