You can get the pregnancy tracker under the Trackers & Calculators link on the upper right. Here's the link for it:
http://www.medhelp.org/trackers/list/98
Or you can go to your profile page (click My MedHelp at the top of the page) and on the right side, you'll see a panel called "Trackers". There is a link in that box. If you click the add tracker link, you'll get a page that lists ALL the trackers available here.
And finally, you can also access it on this page:
http://www.medhelp.org/land/pregnancy-calendar