You are normal Makeen! Don't worry about it! You will do just fine. I doubt the girl will have any complaints if you just concentrate on the topic at hand and forget about the shape of your little guy.
Don't worry about your boyfriend much. When the time comes you will either know or you won't if it is a problem for both of you. If it doesn't work out, it is not the end of the world. There are solutions, but I doubt it will cause a problem.
Of course, you can also both turn to a position where you are 90 degrees perpendicular to each other so that relatively speaking his penis will be pointing up or down inside you. That is, you on your side (spoon) and him upright on his knees.
Imagine that! I finally put my advance mathematics from my engineering degree to good use after all these years
Math word problems... complete with solutions.