Is the dick too big??

So, to give you the picture my boyfriend is 6ft 3 and I'm 5ft 3. As you can probably tell from this he's pretty big. He was my first as I was his but we've been having sex for over a year now. 
I'm wondering is it normal to still hurt sometimes? I mean it took us a while for it to not hurt because of both his and my size. But it still to this day can hurt if we haven't done it in a while or if we do it in certain positions that go too deep (e.g. Missionary with legs up) I'm wondering is this normal or is something wrong with me? 
I can't really compare how big he is because I've never experienced anyone else so I don't really know.