the cervix is usually only around 3 to 4 inches away from the vaginal opening. What happens during sex is that when a woman gets aroused, the cervix will retreat higher into the vagina to allow space for the man to enter. so while men go through a physical change of erection, us women go through a change also, only it is internal. so if you're having a lot of pain, make sure that you are relaxed and aroused before he enters you.
u might also have a UTI or a bladder infection. the sour smelling urine and the pain are symptoms of that. does it burn when u urinate? do you feel the frequent need to pee without actually going?