Call and get emergency assistance.
In answer to your worries
• I already have 2 young children and due to DP’s job I am basically raising them as a single parent
That is tough, but in for a penny in for a pound. Talk to your Dp about how 3 means he needs to carve out time to help
• I have a health condition so worried what the exhaustion of having 3 would do to me
Maybe hard going for a bit but it will get easier and the love you will get back will improve your heart health
• We live in a small flat (imagine family of 5 in a small flat….)
Things change, as time goes on it's likely you will find a bigger place if not it's still manageable until the baby is 3
• We’d need a bigger car
Yep.
• I had extreme guilt that my two would feel left out and not be able to have much 1:1 time with me (especially in the early days with the hours and hours of breastfeeding)
They won't if you can include them as Mummy's helpers or just co sleep with them
• I cosleep with my two.. I could not co sleep safely with 3!!
Totally fine, humans have co slept as a family with more than 3 for millennia
• I always suffer horrendous morning sickness, this would really effect my parenting
Mmm that is a bit of a worry
• I am generally just so tired as it is
You'll be as tired as tired can be for a while. You will have 3 kids though. Amazing 😻 sleep later
Gosh I hope this works out for you
Good luck