Has medical progress stopped human evolution?
Not at all. 


Mutations accumulate independent of medical progress. In fact harmful mutations which would otherwise cause an individual to die can now be "cured" thus if anything increasing the gene pool. 
Typically medical progress extends our lives when we are much older, thus we have already passed mutations on to our children before a bottleneck in evolution could occur
We are getting taller, less hairy and women are getting more attractive which is another form of evolution
As new diseases develop the selective pressures on humans are ever changing. HIV which was never as widespread is now pushing certain immunogenetic traits to be favourable, the same is true for malaria (HLA 5701) and many others


In conclusion, whilst there are fewer and fewer strong selective pressures forcing extreme evolution, our bodies are designed to evolve slowly unlike viruses like HIV. Our mutation rates are around 1 in 10^9, allowing us to always slowly evolve as there will always be traits which are slightly more advantageous.