We have had very pearshaped ladies on here who turned out not to be pregnant and girls who are barely showing who were, so I have given up judging just from pictures! mallethead
If you can find a good exotics vet (with experience in small animals rather than a general vet) you will probably get a better answer. However, even he won't be able to tell you anything in the first half of the pregnancy! Piggies won't really show until the last 2-3 weeks of their pregnancy, and until then it is sadly a waiting game.