Trying to hold my head above the water

My 4 year old has always been a very testing child. Besides having a speech delay, he also has huge tantrums that are quite frequent and can last up to an hour. He will scream his lungs out and cry without stopping when something very minor happens or he wants something his way and I don’t accept. It’s just become a lot lately to the point I’m also crying with him. I know it freaks him out cause he goes quiet and I don’t want to scare him but I just don’t know how else to cope. I also have a 16 month old and I’m 18 weeks pregnant. My husband is at work alot of the time. My son attends daycare 2 days a week in which he is great, his teachers say he’s very quiet but he follows instructions and he’s a good boy. We are going through gov funding to get mental psychiatrist help for my son so he can learn to regulate. Today he had a huge tantrum at my mums because he wanted me to carry him while I had my toddler with me. I can’t cope with his tantrums anymore and I’m truly so so sad and feel like my life has become a horrible joke. I suppose I just need to vent.