it is ABSOLUTELY possible to be XY, and have a uterus ...although, they may find the 'ovaries' to actually be testis....just that they were not able to decend. Or, they may be ovo-testis....a combination of ovary and testis. Usually, this is caused by a defect in the ability to produce, or, respond to MIH/MIF - Mullerian Inhibiting Hormone/Mullerian Inhibiting Factor, although, if the gonads are ovo-testis, it is probable that there is just too much 'female' in you to allow you to have permitted the testis portion to have any effect...also caused by AIS.
MIH/MIF is a pro-hormone is produced by the testis as they begin to form, and is critical for the regression and sublimation of the uterus, cervix and 'superior' vagina (internal vagina), and the decent of the testis to the scrotum in an XY fetus. It is interesting to note that MIH is a form of androgen - of which testosterone is just one of the more known forms of androgen. Since your doctor believes you are AIS, it is possible (probable) that you are unable to react to Any form of androgen, thus the retention of the mullerian ducts, and the retention of the gonads inside the abdomen. Combine this with the possiblity (probability) that your X chromosome is simply more 'powerful' than the Y, with the result that you are a full female...just that you have an 'extra' chromosome, that was not effective - at all.
The syndrome we are talking about is called "PMDS" Persistant Mullerian Duct Syndrome, (a well documented syndrome, although, not widely discussed -can you imagine!) However, in your case you also have CAIS - Complete Androgen Insensitivity Syndrome, and as a result, you could not develop a scrotum or penis - the genital area remained/developed as female, thus you are a female in every sense of the word...just that our society cannot accept the concept that you can have a 'Y' - and still be female...they are under the mistaken assumption that because you have a 'Y' chromosome, somehow you are 'male'....at least to their uniformed minds.
I happen to know a fair bit about this issue, as I too was born with a uterus...and one ovary, along with a lower vagina. But, I also had one testis, and a penis - I have PMDS and PAIS - Partial Androgen Insensitivity Syndrome. The doctrines dictate that if an infant has a 'viable' penis, it should be assigned 'male', regardless of the karotype!...so they assigned (mutilated me) as 'male'; (at 6 months old they removed my uterus, stuffed my ovary into my scrotum, and sewed my vagina shut - they then submitted me to approx 2 years of testosterone treatments)....however, like you, my body is more female than male, and about 5 years ago my body re-established the ability to produce estrogen, and has since gone through female puberty....at 46!
I do wish you all the best....you have a wonderful life to look forward to .... motherhood...(and grandmotherhood!) And be grateful that you were born the way you were .... without any 'ambiguity'...this would surely resulted in you being mutilated much as I was - and many others.
Some good links;
http://www.emedicine.com/med/topic1702.htm
http://www.emedicine.com/ped/topic1492.htm
http://www.worldhistory.com/article....rian%20hormone
http://www.hopkinschildrens.org/spec...ersex/sd4.html
http://www.thedoctorsdoctor.com/diseases/pmds.htm
http://radiographics.rsnajnls.org/cg.../full/23/2/309