Pregnant and depressed with a toddler

I'm struggling today and finding a lack of support from my usually supportive husband who is having a difficult week at work. I'm 26 weeks pregnant with my second. Have an almost 2 and half year old who is a burning ball of energy. I've started on antidepressants with help from my doctor. The last few weeks I seem to have leveled out with out so many ups and downs but this last week I feel like I've slipped back. We just put my son into a big bed and he's challenging it as expected but I'm exhausted. Yesterday I felt brace and took him for a walk with him riding a balance bike for the first time, it was a success and I felt good. But today he woke early wouldn't go back to sleep and I'm tired. Right from the get go I've not felt like engaging him and he picks up on this. He acts out when I'm feeling like this and I know it's because he picks up on what I'm going though. I can't stop crying, just want to rest, no idea what to do with him, the weather is crappy and all my family are working. There's so much I need/want to do and I have zero motivation. Has anyone else experienced depression in pregnancy? I feel like there's no way I can handle another baby with the way I'm feeling