My ds has one almost the size of a golf ball above his left eye. It was invisible at birth, then he had a little "herald patch" which looked like a little bruise, then a flat red patch, then it started to bubble up and once it reached this stage, it grew quite rapidly until he got to about 12 months. It stopped growing abruptly and stayed the same for a few months. It may sound trivial when so many children have terrible problems, but it was quite horrifying watching it grow and not knowing if or when it would stop.
The "involution" (shrinking) phase started a couple of months ago, and it is now significantly flattening out in places and has grey/white patches. This is characteristic of an involuting strawberry mark/haemangioma.
I tried very hard to get better care than just observation from the GP. Using histrionics, tears, threatening behaviour and general perisitence I managed to get him seen by several different surgeons and discussed laser surgery, steriod treatment. Steroid treatment is only used if the mark affects "function such as sight or eating - this was a possible issue for us, but won't be for you. Laser treatment used to be the standard treatment until a small study in Birmingham a few years ago found that it wasn't effective. I have found plenty of research to the contrary and am not convinced, but NHS policy is now NOT to offer laser surgery unless the mark has ulcerated. (this is very uncommon, and usually affects the really massive ones that cross skin folds, don't worry.) He is seen regularly by a consultant opthalmologist to assess the possible impact on his sight, and by a plastic surgeon because it is possible that once the final involution is complete, some plastic surgery will be offered to "tidy up the scar".
BE PERSISTENT, do not be fobbed off by your GP. You should see a consultant paediatric dermatologist and make him measure it every month or so. I had to fight for this but I did get through in the end. If you look up your local big hospital on the internet and find the name of the head of paediatric dermatology, you can request to be referred to him by name. It would be quite difficult for your GP to refuse that. THEY should take photographs in the hospital and keep a file monitoring its' growth. I also read everything I could find on the internet about haemangiomas (strawberry marks) so that I would know what the doctors were talking about (and whether they were flannelling me!).
Apparently the statistics for complete involution are:
50% by the age of 5
70% by the age of 7
90% by the age of 10
They are all different, and do different things at different rates, but most of them do disappear. I hope you get the information and support you need.