I would go back to your GP and if needed ask for a referral to see a Dermatologist

If you can, take a stroll around somewhere like DJs and/or Myer. Ask every single cosmetic counter for samples of their products. I think a good cleanser would solve your problem, but you really need to try them to work out what’s good for you.

I used pro active when my face was really bad and it helped so much. My skin was great!
The only thing you have to watch out for is the moisturiser isn’t strong enough to keep your skin from drying out. I used drunk elephant to help keep my skin moisturised.

I started getting IPL treatments which have seriously helped with my postpartum acne and remove the scars and pigmentation. They say it takes a few treatments to see results but I noticed a difference after the first treatment.

Have you talked about it with your GP ?
I don’t have experience myself. Maybe this article helps you in the right direction
https://www.healthline.com/health/postpartum-acne#treatment