Hm, I think doulas are absolutely wonderful, but you definately need someone you can be relaxed around so you can accept their help. Otherwise it will possibly end up being more stressful on you as you feel awkward with someone else helping you (I know this feeling....I feel a bit guilty about someone else helping me).

If you think you can get past being uncomfortable about the help, I would say absolutely go for it. A doula is not only there for emotional support (which it sounds like you have covered), but practical help as well- which with two other kids I am very sure you could use!

Anyhow, that's just my experience with a doula- an actual doula could probably answer you better!