So Here I am pregnant. Never thought I'd find someone who would complete me so wholly; but here he is- and we are having a baby!!!! 8 weeks along, and we are getting ready to move in the next five days. YEOWSA! Haven't been working out as much as I would like- the puppy dog is feeling the lack; but we have been in a FRENZY getting things packed to do a cross-country move.
It's extremely rare for a preschooler to be clinically depressed, unless something seriously traumatic has happened. It sounds more like your son is just vulnerable to getting bumped into a bad mood, and that it's harder than one would like for him to climb back out of his slump. And he sounds very normal; lots of other kids have similar tendencies. So what to do?
Exercise during pregnancy helps to alleviate many of the common problems of pregnancy. It improves circulation (which helps prevent constipation, hemorrhoids, varicose veins, leg cramps, and swelling of the ankles).