I'm posterior, about 50% effaced I'd say. I don't want to irritate myself too much so I'm not checking on dilation...plus it means nothing for me. My cervix is quite far behind baby's head....it's so low that I can feel 3+ inches of head down there...yikes!
Day- If you sit on the toilet(I find this the easiest position) you may need to insert your entire finger before finding your cervix. It will feel like a donut shaped area about the softness of your nose. It will most likely be located towards your back.
Kate- you're probably feeling the shoulder as the head should be right above the pubic bone...if your mw can feel head through the vaginal wall:) Or baby is curved around toward that side and you're feeling the lower, back of the head....?