You certainly don't want to ignore something that might be a problem. Either your OB or your family doctor could help here -- I'd choose the one you feel like you have the best relationship with.
Also, some friends have had scary experiences with anti-depressant drugs, so I might ask for a blood test to check your hormone levels and other things before diving into any prescriptions that might have unwanted side effects. A blood test will show if progesterone, insulin, blood sugar, thyroid, etc. are in the normal range. Honestly, low blood sugar and thyroid issues can cause serious energy and mood problems, and they're both easy to fix. Also, if your iron levels are low you'll feel run down a lot.
I'd also pay attentin to your diet. It's hard to eat right when you're a busy mom, but there are some easy ways to adjust what you're eating that might help your moods. I'd drop caffeine all together. Granted, you might be MORE grumpy/moody for a few days after you quit, but that will even out. Make sure you're not snacking on things loaded with sugar or even worse, high fructose corn syrup, which causes peaks and valleys in your blood sugar levels. Snack on a piece of fruit instead of sweets, use honey in your tea instead of sugar, etc. Other changes -- replace refined grains with whole grains, stay away from red dye and MSG (monosodium glutamate), and drink plenty of water.
The idea is that a lot of processed foods and artificial things cause our bodies to behave as if it's being invaded by foreign objects. Red #40, high fructose corn syrup, and disodium EDTA were never meant to be in the food chain, and your body knows it!
The other thing that has seriously impacted my moods is regular exercise. I never went to a gym or anything until the beginning of this year. I found one with free onsite childcare and try to go 3 or 4 times a week. I think a regular boost in the body's natural endorphines helps keep me more even and less prone to volatile ups and downs...and certainly less of the "down" times, where you just feel "blah" and unmotivated. Of course the problem with being unmotivated is that it's hard to get yourself moving to make this particular change. But, I did it with a friend and now that the habit is there, it's easier to keep it up (and not to mention the fact that I'm PAYING for the gym membership!)
The other thing, of course, is sleep! I have to check myself when I start complaining of being tired....If I've been up late several nights in a row, then up early with the kids, OF COURSE I'm exhausted. The body can't run very effectively on 5 or 6 hours of sleep a night. I've also heard that the deepest sleep you'll get is between 11pm and 3am. If I'm not going to bed til midnight, it doesn't matter if I sleep til 9am, I missed out some of on the most restful sleep I could have had.
Anyway, there are tons of things to think about :-).
I hope you get some relief soon!