Welcome to the forum
We aren't professionals but we do have alot of experience with depression, meds, counslors etc.
You certainly have alot on your plate-I would be anxious too. First, take a few deep breaths-lol. OK, your precious baby will be coming soon. First of all, you have massive hormone storms going on right now and will postpartum. If you are not breastfeeding, I would seek meds and counseling. Wherever you live, they will have a sliding scale mental health clinic (try calling Family Services or mental health for a name). These clinics should have a psychiatrist for meds only and counselors. I and my daughter are going to one right now and They have not asked for a dime. I used them several years ago too and they were great. Also, if you cannot afford scripts try pparx.com for cheap or free scripts. Right now, Catholic Charities fills my scripts for free because of low income.
Even if you breastfeed, you can get counseling to help you sort out your thoughts and options for now. Your son should be able to get help also. My daughter is doing much better between some meds (no more) and a wonderful counselor.
Right now, try to focus on having that beautiful baby and taking care of the 3 of you. Feel free to come and vent whenever you want. Let us know how you are doing. I have a feeling that things will work out for you-remember who is important in this equation and that is you and your 2 kids.
Keep posting and take care