I think there was an earlier post that would be really helpful for you here- about what your plans are to change things.
You have spent the past several years in constant flux, and I would suspect THAT, more than anything else is going to cause you to struggle with anxiety and depression. You need to create the life you want.
If you are going to be staying where you are, fine, but commit. It isn't fair to drag a child with Aspergers all over the place, to make him move repeatedly, to cause chaos when he most needs stability. It just plain isn't fair. I also have a child with Aspergers, I promise, your whole family- and particularly this child- will truly suffer if you don't set down LONG TERM roots soon. Pull it together for him if you can't do it for yourself. If you aren't going home next week, commit to staying where you are for a few years at least. Send for your belongings and give the kids the toys in their new home.
Dealing with depression and anxiety without meds is completely possible- particularly as you only have a few months left until you deliver. You will be feeling overwhelmed right now because you stopped them the wrong way, but since you've already done that damage- stick with it. Put a schedule in place and force yourself to clean/cook/parent. You won't necessarily feel great, and you will have days where you struggle emotionally, but you have other adults in the home to lean on for support, at least until you can get in for a new evaluation with a new health care provider who can help you choose to medicate appropriately (or not) based on their evaluation. If you are really struggling, contact your local mental health clinic and explain that you are in crisis. Chances are, they will refer you to the ER for assessment.
You posted in personal growth- sometimes you won't just get support there, because we want to see you step into being a healthy and whole parent to all of your children. We know you are able to get there, you just have to get out of your own way and do the uncomfortable stuff to do it. Put your foot down and say, "this is where we live, we will reevaluate this in 3/5/10 years, but not before." Register for all the services you need to have support- if you don't have income (have you found jobs?) apply for TANF and SNAP along with WIC. Inform your son's father of your relocation, and provide him with a way to contact you. Set firm boundaries with your parents, but let them know how to contact you in an emergency. Establish prenatal care, and have your records transferred. If you have been on Medicaid and meet the standards within the state you live in, you should have expedited coverage- a matter of days- at most.
It sounds like you have an opportunity to start fresh here, but do it in a healthy way that will benefit your family in the long run. Make a commitment to yourself and your family that you are going to create stability instead of upheaval, consistency instead of insecurity, knowledge instead of anxiety, comfort instead of fear. Talk with your children about their new long-term home, and explore the town. Make friends when you take the kids to the park, but make sure you are choosing people who will be a strong positive force within your life.
You have more power than you give yourself credit for. You can protect yourself and your family from your crazy parents by setting boundaries. You can create the stability your children need, and the only thing you have to do is to say "this is the way it will be!" Please, believe in your own power to create the life your family deserves. Demand excellence of your partner in his support of the family and the goal for long term stability of the family. Recognize the harm you are causing your family through your acceptance of chaos, and decide it's time to change that pattern. Your son is still young- while he's been through more than any child should have in his few short years, there is time to start healing the wounds and move forward.