I was so tired and lifeless with second preg too... mentally OK but physically blah... then strangely enough with third preg I've been full of energy and really well almost the whole time... not now that I'm 36 weeks tho! I think hormones have a lot to answer for, more so than how much you have to run around after a little one, because in my case it was just completely illogical.

Blame the hormones. And if you feel like you're a bit depressed rather than just tired and over it, then get it checked out with the doc or OB.

Hugs.