If its anything like Marta, sometimes she looks half starved and nothing in her womb but the next day she is so so big again, oh and Marta is due 2nd week of March, last yr I was convinced she was not in kid until the vet came by middle of Feb to do shots and asked me when she was due, as it looked like she was, yup she sure was, and had 2 very big kids, what I am trying to say is....they hide it very well sometimes.
Surly with an Alpine she should not be in heat this time of yr? just a thought.