Dear OP,
I have been in a similar situation myself when I was younger and I had 4 children under 6 and with a partner that worked full time with travelling to work. I was overstretched and (probably) also with undiagnosed autism (I will get an assessment later this year). I was so full of rage and sadness and completely overwhelmed. I didn’t know what to do, and this overwhelmed feeling came out as shouting, lots of times out and feeling awful. I took them to the supermarket once and they were literally rolling melons down the aisle and I wanted the earth to swallow me whole.
The worst part was my trigger, and I didn’t realise this was an autism trait until I was older. I used to fall apart if I had an aim for the day and it was cancelled or didn’t work out the way I wanted it to. For instance, I would plan to go for a walk around the lakes, but with small children I had to change nappies, feed them, feed me, change them, chase them to put on clothes and shoes. Sometimes it took so long that by the time I was done it was lunch time! I had a few times where I fell apart at the door, crying and realising it was lunch time and then nap time, and it was too late. It was horrible. This would lead me to a depressive spiral for the rest of the day.
Add on the other problems - feeling overwhelmed trying to talk to other mums in baby groups, trying to tidy a house with children trashing it behind you. Not being able to keep to plans because it was hard to leave. The noise, the smell of nappies and wee, no personal space and no time to yourself to re-balance (even on the toilet).
I am older and over the worst bit, but still remember the struggle. It is a good idea to take each of your triggers and pinpoint what it is that is making you so overwhelmed, and find a way around them (if you can).
Maybe it was just me, but being a parent with autism (also ADHD with me) is bloody hard. When you are struggling, and you sound like you are, you have to think about your children and ask for help. Do you have any family or friends to talk to? I have always been awful asking for help, and in the end I was depressed for years.
Good luck OP, I hope this helped.