20 weeks and feel low, tired and have bad back

[char24]

God I wish the next 20 weeks would fly by, I have a 22 month old who is just showing signs of cutting back day time sleep but is now waking at 5.30am everyday so is he over tired? at a loss?
I have had bad congestion since i first got pregnant resulting in broken sleep due to a dry mouth and sore throat most nights.
Due to the above i am exhausted, before xmas got so tired ended up with bronchitus- any ideas re sleeping etc.. i am starting to get depressed and short tempered and thats not far on my 22 month old . help?

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Thanks for the advice, i made some changes to dc sleeping arrangements, the heating comes on an hour earlier and on one of my night visits to the toilet i am putting an extra blanket over him and it seems to be working, unfortunately he also now has a cough and cold so is extra tired so that may be playing a part.
I used to go to the gym 3 times a week but have let it slide as have been so bungged up that i just have not felt upto it. I do understand your comment re making you feel better, it does its just dragging myself there and now getting a place in creche as eveyone is on mad new year get fit missions.
I am considering the docs as it cant go on but midwife just keeps saying its normal!!!! I am trying to eat well, as with last pregnancy felt sick as a dog for the first few weeks but not too bad now