ANSWER - I don’t mind telling you that the first thing I did after reading this question was to conduct some research as to whether an eleven month gestation period was actually possible for a human. It turns out that it is but it is rare. In many cases of unusually long pregnancies the woman has actually had a very early miscarriage and then conceived again without realising.
(You did mean Litha and not Lammas I take it? The period between Lammas and Beltane would be a much more usual nine month pregnancy)
Accepting that you didn’t make a mistake and that the pregnancy did last eleven months, I wish you had given me a bit more information as to why you believe this to be significant. Is it the length of the pregnancy, the date of conception or the fact that you were born a few days after Beltane that you are attaching the significance to? I’ve got to be honest – I think this is a case of mistaking coincidence for significance. Many people are conceived on Litha (and indeed all the other sabbats) every year but that doesn’t mean much beyond the fact that their parents chose to make love on a particular day. It's the same with giving birth – the sabbats are no different to any other day of the year. It may be nice for a witch to be born on a sabbat but there is nothing to suggest that a greater proportion of witches are conceived/born on sabbats. And when you start stretching it to being born “near” rather than on a sabbat any claim to significance just becomes too tenuous to be workable.
This does work the other way though – the fact that the date of your birth is irrelevant doesn’t mean you don’t have a genuine calling to witchcraft or whatever individual path you choose to pursue. I’m not knocking your calling, I’m cautioning against looking to find patterns for the sake of it. The simple truth is that some things do happen for no reason and as witches we need to accept that.
I’m extremely sorry to hear about your mother’s cancer and I hope she went on to make a full recovery. I’m glad you sound so positive about your journey of self discovery and I wish you all the best on your path.