Feeling super stressed out

I honestly feel like crying and breaking down. I'm trying so hard, but I'm exhausted. My youngest son is hitting the terrible 2s were he wants to test boundaries. I've been trying to get him to nap, he refuses. He's been having a lot more tantrums. He seems to just want to play and not sleep. He's also randomly decided not to eat anything I make him. He just randomly became picky. My eldest son is 15 and he has been so mouthy lately. I think a lot of it is because school is stressing him out. He isn't doing well in the distant learning and he's getting more frustrated. He also has really bad dermatillomania, which is a mental disorder that causes him to pick at his skin. He usually picks at his feet. His feet are so bad he is having trouble walking and his therapist hasn't been much help. She will go weeks without talking to him and she's hard to get ahold of. I can call her and leave her texts and she will never get back to us. I finally got a hold of her yesterday because my son was just being so much. He gets really mouthy with me, so I send him to his room. The reason he was upset was because he didn't do very well on an essay be wrote. While he's in his room he picks at his feet so bad he's bleeding. I got a hold of his therapist and she asked how he was and I said he hasn't been doing well. He's been mouthy, getting frustrated and his dermatillomania is getting worse. She tells me I need to learn how to balance time with my kids and I'm being a bad mom and I'm allowing him to continue to pick at his feet! I hung up on her! I'm trying to balance time with my kids! My 2 year old is testing boundaries and I'm trying to handle him and I do tell my son not to pick at his feet when I see it! If he's doing it in his room how am I supposed to know. My husband isn't home that much anymore because the hospital has been making him work all these extra hours. He's stressed because the hospital is overflowing with Covid patients and he's worried about bringing it home. I miss my job but it'd closed again. I know its to keep everyone safe, but being able to leave the house and work helped with my mental health. I feel like an awful mom because I can't get my toddler to sleep or eat. And my oldest is obviously stressed out to the point of picking his feet raw!