Normally, you would dress a pregnant woman as first an H shape (if she was an X to start with) and then go to an O shape as her stomach expands. As a proportionally very long body and short legs X, you will find that you need to take your proportions into play when dressing during pregnancy.
Unlike the traditional O shape who tends to want to make her stomach look smaller, pregnant women are usually happy to be seen as pregnant, so don’t feel it so necessary to take away that focus on the stomach.
Dresses and skirts make your legs look longer as we don’t know where your legs start. Either try knee-length or maxi length.
Wearing copped jackets and cardigans over the top of your longer maternity tops will draw attention up your body and visually balance your shorter legs.
Skirts that end around the knee with a long top will give you the appearance of longer legs.
Try layering tops or using a belly band to wear under regular length tops. Layering will shorten your body to balance your legs.
Why not belt above your bump? You can belt over longer cardigans and tops to shorten your torso and draw the eye upwards.
Don’t forget to add some larger scale jewellery to draw attention up to your face.
For some inspiration I’d suggest you check out these pregnancy style posts on Academic Chic who show a range of great pregnant X shape styling. Or Nic at Domestic Sophisticate who also has lots of great style ideas for pregnant dressing. And Teal from Expecting Chic also has great style.