You are applying for a fiance visa, correct?
The fiance visa does not allow any free access to the NHS (as it is valid for only 6 months), so you will be required to purchase health insurance to cover you for the time you are on the fiance visa. I'm not sure what health insurance policies/companies are good, but maybe someone else can help with that.
Once you are married and have been issued with the next visa, FLR(M), you will be entitled to 'free' healthcare on the NHS, so you should be able to get your required medication without much trouble. I say 'free' NHS healthcare because when you apply for FLR(M), you will be required to pay a £500 NHS levy to allow you 'free' access to the NHS (also, if you will be working in the UK after you get FLR(M), money towards the NHS will be taken out of your taxes).
Once you have paid the NHS levy, all your healthcare will be free at point of service - you won't need to pay anything for doctor's appointments or hospital stays and you will only pay a small fee for prescriptions - about £8 per item on the script in England (but all prescriptions are free if you live in Wales or Scotland).