Is it normal to feel this way?
Pretty much. I don't even know if by "go to the bathroom" you meant one or two, but it hardly matters all the relevant structures are packed very tightly in there. Something pushing into your vagina is putting some pressure on both your urethra (in front) and your rectum (behind), and the unfamiliar sensation can certainly read as bathroom-type urgency of some sort, even if you've recently been. I'm going to assume that you are A) young, B) tight, and C) just generally built small. The first two will pass, as will the unfamiliarity. What never does change is the requirement that you be quite turned on before he tries to get in there. It makes a world of difference. You'll be amazed how much more space there is for him when you're ready to receive him. Slow. Down.
See Andrea's other column at carnalnation.com.