Hi there, How are your numbers after meals? Is your diabetic antenatal team happy with your control?
Honestly, I know this isn't very helpful, but I would take every chance you have to sleep now. The weather is so hot which is tiring in itself, let alone when you're growing a baby. All the hormones, and now you're growing bigger makes sleep more difficult. I don't think I've had unbroken nights sleep for over a year, as I started waking regularly in e night from about 20 weeks just being uncomfy/loo runs. It's tiring stuff. I should think the anaemia is not helping either- I know I am struggling with tiredness now as I am anaemic from the birth. Fingers crossed you will go back to normal once baby arrives (obviously apart from the general sleep deprivation), though from experience it took a good 12 weeks after for my hormones to start to become normal again.
Do you see a midwife as well as the diabetes team? Maybe you could have a chat with her/him about it. Do you think you could be feeling a bit depressed, as you say you're not yourself, or do you think that is down to feeling so tired? post natal depression can start before baby is born. Are you worried about the pregnancy, as that can be very draining as well.
I wouldn't worry about feeling exhausted, I would rest as much as you can. I felt out of breath during pregnancy as baby grew (they reckoned my monster was 6lb already at the 24 week scan!), and his bum/feet were up in my ribs hence not much room to breathe.