Having a hard time back at work:(
Sending you a big hug Callahansmama. It is a tough adjustment. I wish some careers weren't so hard to get in and out of. I think it is totally normal that you are experiencing less enthusiasm for your job. Half of you doesn't even want to be there (maybe more than half!) It sounds like you are holding yourself up to the former standard you set, and perhaps that just can't be right now. I bet you are a pretty dynamic teacher! You can't pour your whole heart into it right now, and that's o.k. You also might have a pretty challenging class---kids are getting more challenging. I wonder if that is the cause of some of your anxiety?
I would accept the 'halfway' feeling of all of it. I think when my kids were younger that is what I had to do. I had to accept my own limitations. Lots of big ideas had to get put on hold. I'm not sure what grade you teach, but I bet you are still pretty awesome even at half strength!
Do you have a good child care arrangement?
Callahansmama - looking back at the time when my children were that small, I think that I just didn't realise how utterly, chronically tired I was. It was the kind of insidious tiredness you get when you're running short of sleep over a very long period of time, which starts to feel like normality because you can't remember what it was like not to feel that way. I wasn't (mostly) actually falling asleep at my desk, so I underestimated the extent to which it affected me - but it sapped my energy, concentration, and motivation to an extent that I can really only see in retrospect. Is it possible that this is what's happening to you, and that this is the problem?
Other things that detract are not having enough me time and enough couple time with DH. Until DD1 was close to 2 years old, there just wasn't enough time in the day. After that it was more reasonable and I could contemplate having another child (though we had twins, so we got two more!) Now with three children while I am still tired and lacking in me/couple time, I know this is temporary as I've been through it before. I'm also better about asking for help from DH and others and since the twins travel well and DD1 travels fine now (not as a baby) we can go visit our families often which also helps a ton.
So if you don't have good support, try and get some. Don't be afraid to ask for help from your partner, I know we sometimes feel we shouldn't have to ask, but also people can't read our minds either, so just ask and don't worry if you should be or not. And ask for help from any family/friends you have around too. Don't forget that everyone needs breaks, I know I would sometimes feel guilty when we had someone watching DD1 because geez I already was missing out on so much time with her, but we all need breaks. So try not to feel guilty about that, even though from experience you probably will. I'm better about this with the twins.
One more thing that helps me is lunch time. I use this time to decompress (reading at lunch is what I usually do as well as trying to take a short walk outside) and to run quick errands child-free. This helps me catch up and relax as running errands without children is really quite pleasant and the reading and/or walk help me to feel like me instead of either Mom or Employee all the time. I also try to do something with my DH a few evenings a week at least, even if it is just watching TV together, so we can reconnect too. Other evenings I just must go to bed early, but I try not to do it every night.