I don't know how low your vitamin D is but when I was eventually given high dose tablets 3 months after my initial results came out, I then felt dreadful for nearly 3 months while on them. (I had actually broken one of my toes by the time I got my results.) I was in more pain than before I was on them. I was on a dose of 60,000IU per week for 12 weeks. I was then told to take 1-2,000IU per day as a maintenance dose until I spoke to someone with MS. He then pointed out considering my background I should do my own research and the research indicated I should be on 4-6,000IU instead until I get my level up pass 75nmol/L.
So I strongly doubt your vitamin D supplements are enough. You want a vitamin D level of around 100nmol/L to be optimal. Depending on where you are in the country some labs state a level of 50 while others say a level of 75 is sufficient.
I suggest you go to your doctor's receptionist and get a copy of your test results with ranges. It is your right under the Data Protection Act 1998 to have a printed copy. The surgery will have a protocol for giving you the results so you may have to wait a few days. They may charge you a few pence for the copy and if it's over 40 days since you had the tests they may charge you £10, so you need to act asap. Once you have the results start a new thread to get more detailed advice.
In regards to ferrous fumerate if you are actually anaemic then again the dose is not enough. The standard treatment for iron deficiency anaemia is 3 tablets per day as the aim is to get your level up as quickly as possible.
One tablet per day is a maintenance dose for people who have had iron deficiency anaemia and are likely to suffer it again due to another medical issue.
The site I have posted links to below is a site lots of NHS GPs use to work out how to treat people, so you can point to it if you disagree with your GP as the information is from what is considered a reputable source. It isn't the best information out there but is a lot better than how your GP is treating you now and better than the NHS Choices site.
Vitamin D information - patient.info/doctor/vitamin...
Iron deficiency aneamia information - patient.info/doctor/iron-de...