It's just so hard

Being a single Mum is hard. And staying calm all the time is evened harder. Especially when I'm getting so tired from being so huge these days. My son cam eback from his fathers today after 3 days away and as usual he came back with an attitude he picked up from his 15 year old half-brothers. So all day he was rude, not answering when spoken too, spitting at me, not doing as he's asked. By the end of day when he refused to do his teeth, I couldn't remain calm. When he didn't do as asked the 5th time I started counting, which he knows when I get to 3 there are consequences, this time it being him going to bed without me. He kept going and I got to 3 and went down stairs and he freaked out, stamping and screaming and yelling. I lost my temper and dragged him to bed and shut the door with him still screaming, and I burst into tears and felt horrible. I'm finding everything that has happened recently so hard to deal with and have been swinging between exhausted and upset so dealing with a screaming child just pushed me over the edge. I had to go back into him room and talk to him and let us say our sorrys and hug. If I'm struggling this much with 1 how am I going to manage with 2 on my own? And the alone thing I am finding so tough already and the bigger I get the harder it all is. I feel like I'm whining but it's the only thing I'm feeling at the moment apart from anger. My head is so loud and even though a friend told me today that I have to be positive going forward it's just too much to deal with to be able to do that