I think my cervix sits quite low based on - when inserting a tampon (without applicator) my finger only goes in a little past the first knuckle before the tampon stops and won't go any further. I struggled with tampons when I first started using them for this reason because I can always "feel" the bottom of the tampon as it seems to sit a bit lower than is comfortable. Now that I'm used to them I can ignore that sensation but wouldn't want to use anything longer than a tampon.
Also, I only use regular tampons not super as the super are too painful to insert (I think my vaginal tissue is particularly sensitive during menstruation). It's no big deal though as on a heavy days regulars last 2-3 hours and I find its manageable getting to a bathroom to put a fresh one in.
For these reasons I'm erring on the side of the shortest and narrowest one I can get. I'm 29 and a virgin - have been waiting to meet the right guy, which I have now, and for my wedding day, which is soon. It seems it would be recommended for me to get one with a width of 43-44mm "small, no kids" but I'm thinking in my case maybe I would be better off with the 40-41mm which is considered "teen size". I'm just not sure on this - whether I should go with my gut because I think my vagina is shorter and narrower than most my age or whether I should go with the recommendation. I'm also wondering if a narrow one will end up loose after I become sexually active?
And, just one last question - some have spoken of leakage when the cup gets full - I'm wondering if this is slow like when wearing a tampon or does it come out more quickly?