Aching, tired, horrible mom

I don't know what to do. The Little Buddy is having sleep troubles. I am so not used to having to deal with sleep issues because he is such a good sleeper. But now I am, just when I am slowly becoming down for the count and really tired with this pregnancy. My back is aching and I'm just plain tired. ACHING AND TIRED, I TELL YOU! Twice now it's been hard putting him to bed. Well, he goes to bed pretty easily but about 20 minutes later he starts crying. We would have no problem letting him cry it out but it's out of the ordinary and he seems scared. I am thinking it's separation anxiety. So we check on him a few times and then he goes to sleep after about an hour. Today was the first day it happened at naptime. I put him down at 1pm and immediately he started crying. I went in there and reassured him and then let him cry for a few minutes and he went to sleep. So did too, for about 45 minutes. The minute I got downstairs to eat my snack in peace and watch Bringing Home Baby he started wailing and nothing worked. I went up, kissed him and left. I went up 20 minutes later patted him, wiped his nose, told him it was time for naptime and left. and STILL he was crying. I went up, sat in his rocking chair, told him I was there, pretended to sleep myself and he just stared at me like I was an idiot. I finally bregrudgingly took him out of his crib. I feel cheated of my own rest time and I feel like a horrible, horrible mom for feeling that way. I told him he had to play by himself while I sit here getting out my frustrations on the computer. It's going to be a long afternoon. I can't wait until the fall when it's not too hot to go outside for extended periods and I'm not pregnant anymore. And I can't wait until he grows out of this (what I claim to be) separation anxiety stage.