I was there few years ago - Generalised Anxiety Disorder (originally PNA, but positive I had anxiety all my life, it just imploded).
OP - it gets better in time. The worst thing to do is to shut off and stop doing things - but I completely get it's scary, draining and exhausting.
You have to sleep more and better - sleep deprivation makes it 100 times worse. Get help with the baby, as much as possible, and rest - actually go to sleep.
Have a look on BHF website for breathing techniques. Do these exercises every day. Take your baby for a walk and do them. Honestly, it is a must.
Good job on the referral to postnatal MH team. Your HV should help too. The MH team may refer you for CBT - it wasn't massively helpful to me, but it might be to you. My NHS therapists said I'd benefit more from compassionate therapy.
Go out on your own, just you - for exercise. Move your body even if gently - gentle shaking, yin yoga or restorative yoga are all helpful as they reduce cortisol levels. But generally regular, gentle exercise is good.
Lower sugar intake and caffeine.
You may go on medication and I'd consider that if you have to wait for a referral. A low dose anti-anxiety medication may be helpful to you.
Other things that can help may be hypnotherapy, acupuncture, journalling and lots of time in nature. Anything soothing your brain is a good thing now.
Trust me, you'll come out of this horrid phase but give yourself time. It won't be tomorrow, but be consistent and take small steps every day.
It helped me once I started thinking clearer to separate my anxious brain from my normal one, I named it Susan. When Susan takes over, I can see it now and I tell her to shut up. She doesn't always listen, but it is much easier to get on with life now. It'll be OK, I promise you. Keep going and get any help possible as soon as you can 💐