DH & I have 3 children already, ages 8, 5, and 2.
I am in a similar situation as you are in right now. DH and I have three kids 8, 6, & 2. After our last one which was a boy finally DH stated he did not want anymore kids. I on the other hand have always been open to the idea of at least another baby. It is so hard as a woman to close that door on your femininity, and say you are done completely (speaking for myself). You seem to be in a better situation since you cloth diaper, breastfeed, and are a SAHM. I don't cloth diaper (wish I did), I do however breastfeed for at least 15 months, but our kids do go to daycare as I work full time. If I had your situation I wouldn't even worry about the financial burden as it seems like it won't be much as a burden.
I do have a mortgage, two car notes, daycare and after school to pay, so the decision is a little tougher for us. I did however get DH to start talking about possibly having a fourth. He asked me if I didn't think 4 was too much. I stated I did not think it was. I don't have a very strong desire to have another baby, but I hate thinking that I am done. I am about to turn 29 in 9 days, and I hate to think that I am done when I have so many child bearing years left in me.
I hope you and DH have come to an agreement you both are very comfortable with. Good luck!!!