Is There a Cure for This?

I have 3 children, ages 9, 7 and 5. My 7 year old is high functioning Autistic. This year I'm going to homeschool all of them. Life is usually a little hectic for us and I'm always sleep deprived. I'm hoping that when they all move out of the house I may be able to catch up on my sleep.
However, in spite of all this, I want to have more children. I want to have a house and car full of kids. I went through baby fever last year and my husband and I were looking into having his vasectomy reversed. For several reasons we decided this was not the best route to go.
Then I got what seemed like the perfect opportunity. A friend of a friend was looking for full-time childcare for her 6 month old baby and I accepted. I thought this would be a way to get my baby fix and then all would be well. I loved this little girl. She was just the sweetest baby. But she did remind me that I really didn't enjoy the sleepless nights and bottle feeding that comes with a new baby. So that really helped with the baby fever.
But I still want more kids. My husband and I both wanted alot of kids when we got married. But after Bubba was diagnosed with Autism we had a change of heart. It wasn't necessarily the diagnosis but what we were dealing with as far as his behavior, etc. My 3rd baby was a surprise. Honestly, I cried when I found out I was pregnant. I didn't think I could handle another baby on top of what had already been dealt out to us. But flash forward 5 years and things look alot different than I imagined. Bubba has come so far. Our family is so much more manageable than I expected it to be at this point. I look forward to summer vacation so that we can spend more time with the kids. I love listening to them and watching their dynamics. I'm ready to add to that. I want to have more kids around to love.
My husband is all for having more kids but his timeline is different than mine. He wants to wait until we've moved and our income is steady and we're following a budget and we're all "settled". You know, sensible guy stuff. And I completely understand his POV. But we've been thinking about adopting, which is a lengthy process. I don't want to be adding to our family when I'm 40. Nothing against being 40, it's just that it's 7 years away. My thoughts are 'let's get things started now and all will fall into place at the right time.' It's the same argument when you first decide to start having kids. If we had waited until we were settled, we still wouldn't have any kids 13 years later. Right now I stay at home to raise the kids. I am involved in their lives. I play with them, teach them, encourage them, guide them. What determines whether or not we're ready for more?
Ideally, I would like to have a little girl right around Sassy's age or a little younger. But I am open to adopting a boy, siblings or even a special needs child. At least we would know ahead of time a little of what we'd be getting into. I don't think I have some romanticized view of what to expect. I know that since we'd be looking for a child who has already been in the system for a few years that there will be, at the very least, emotional problems and possibly mental or physical problems as well. But I honestly believe I'm ready to take it on. I want to add to our family and there are thousands of children who are desperate to have a home. How can you argue with that?