L.R.
I don't remember being moody at 5 weeks--I was too tired! But since it's probably hormone related (you're pregnant, so go figure), you could try using supplementation to help it out. I know a lady who had really bad mood swings due to hormone imbalances, and she started taking this one multi-vitamin/mineral supplement, and it all went away--better even than when she took hormone pills, which only controlled it to a point. It's called Vibe and you can get it here: www.vibeforme.com/getbetterhealth. I personally take it and would highly recommend it. Talk to your doctor--you might find that they'll let you take that instead of your prenatal vitamins, and since it's liquid, that will be a whole lot easier (I wish I'd known about Vibe when I was pregnant! I couldn't swallow anything bigger than a pea for the first trimester, thanks to morning sickness!). It's much more absorbable than pills anyhow.
Hope it helps!