WOAH!
OK that is a lot.
Positive bits first:
YEAH you are PREGNANT!
YEAH DH heart surgery was OK?!
YEAH - you have somewhere to live and a house that is being sorted.
Your priorities are:
Yours and LO health
Your home (with DH)
Your fiscal future (with DH)
The rest is NOT YOUR PROBLEM and thus you don't have to spend any time energy and effort on it right now.
Get yourself on to Martin's MoneySavingExpert web site and take a long hard look at your finances - work out where you can cut down / back / out and get your budget going. This will put you in control and so you can make decisions. it will also let you and DH know what action needs to be taken.
Are you sure the tax bill is correct? If necessary get some professional help on this one make sure, then phone HMRC and explain what you can afford (DON'T USE ALL YOUR SAVINGS RIGHT NOW). Please note this is after you have worked out the afford bit from the MSE bit above.
You need to do this sooner not later I am afraid. If only for your own peace of mind. But also paying it back slower time to HMRC needs planning and their agreement.
Unless your insurance is due right now, forget it, you cannot do a thing about it yet. And even after a serious water issue you can always get insurance, and it is not that much more expensive speaks the voice of experience here Concentrate on the fact you are getting the house put right and you have somewhere to live and YOU ARE PREGNANT
Speak to HV or get a private scan if that is what you need to feel OK. Then remember you are strong and taking care of this LO so start being kind to you
Also talk to DH - he is probably in the same boat as you and panicking nicely but not wanting to worry you with a good panic - you are both in this so take advantage of the support there!
You will be fine, asPTFS said above - one bite at a time