Feeling guilty for losing it

I'm really new here. I have a 6-year-old son with autism, a 10-year-old daughter without autism and it seems a husband with autism too.

My son is a great kid. I love him to pieces. He is funny and loving, just like his dad. Just as his dad, he cannot cope with negative feelings from me. I have tried to be always calm, never angry and always loving, as they need me to be, but sometimes I'm so tired, so exhausted , and I just want them to give me a break from their needs. Then I shout and I feel awfully guilty afterwards. I see those buddhist monks and I think "God, give me something of that because I need it".

My daughter tries to help me and distract her brother from me when she sees me overwhelmed but then I feel guilty about that too. 

Mostly I'm ok and my little family is a source of joy but today it was one of those days where my son was tired and he needed my undivided constant love and attention without the most minimal sign of annoyance. After a full day of keeping up I just wanted him to go to bed and I lost it after 6 times of sending him to bed. Obviously he cried and I felt guilty and awful. My husband was my husband. He cannot cope with this. I know he loves us but he cannot cope with it and he tends to make things worse , soo...

Honestly  my husband doesn't understand why I haven't run for the hills. Not planning but has someone an idea how one becomes a buddhist monk??