My experience is sort of like yours so perhaps you'll find this helpful.
I had my baby in mid-September 2009 and started to receive WTC and CTC of about 145 pounds per month, based on a salary in the low 20s. I also began receiving Child Benefit, which you will definitely get. My husband was also not working but as he had just completed his PhD and we had some savings, was not able to get any jobseeker's allowance.
I finally received my tax credit renewal form in May and because of my pay being significantly lower from the previous tax year, my credits about tripled. I am in the USA on holiday and haven't seen the whole breakdown yet but when I used the online calculator, this was about right (husband still hasn't found work, still not able to claim anything). I'm pretty sure that you cannot get this until the new tax year, as your credits are based on the previous year's income. If you haven't changed jobs, you won't really benefit from this until the following year (if the Tories let us!)
I'd never claimed any kind of tax credit or benefit and was new to this but phoned in and they told me I'd done this correctly. Unless you are entitled to more b/c of your husband's situation, I don't think you'll get too much more. I had the same breakdown of pay from my employer and only really saw it drop dramatically when my baby was 4 months old, as you get 50% + the SMP for the 12 weeks.
Hope that helps!