Weight gain like whoa!

So I finally have some energy back and am getting back into the groove of my exercise routines to a degree.  I also don't have many food aversions anymore (11+1 here).  I noticed I lost about a pound over the weekend and just like that, gained 3 in 3 days.  What!!?!?  I wasn't that concerned early on b/c I was loosing rather than gaining.  Now I don't want to start packing it on quickly because it will start to get crazy in the 2nd and 3rd trimester.  Anyone else thinking how to keep this in check?