Oh hun, how frustrating! Firstly I don't have much advice but when through a similar thing with DS from 5 weeks through to 5 1/2 months, so about 4- 4 1/2 months. He was the same, get a cold and not improve fully, get slightly better and then bam, get smashed back to where he was a week ago. It is so awful to watch them when you don't seem to be able to help them at all.

The only thing on her little side is she does have the ability to mouth breathe being that little bit older but gosh, so hard for you both! The only other thing we added to what you are doing is nice warm steamy showers and let the water beat down on her little back. I don't know if it helped but it I do think it seemed to get some of the mucous out. I also swapped the saline drops for saline nasal spray. Wasn't pretty at first but it wasn't causing distress either IYKWIM.

Now, the teeth. Swapping from DS to my DD, she was the same as your little one too. 10 1/2 months before a tooth popped through and they seemed to take forever to become 'full sized' teeth. Once they started though they just popped up all over the place

Sounds like you guys have had a rough couple of months having said all of this though if things don't seem right and you aren't happy with your GPs answer, keep going until you find someone who will listen. You are her mum and no one knows her better.

Hang in there!