Question of Distribution Fitting ?

I have a data which looks like a mixture model and, which fit the distribution function "f(x)=g(x)+h(x)". The mixture model has two peaks one peak amplitude is 10^4 (at x=10) and other has 10(at x=1000). How can I fit f(x) by taking the whole data. If I fit f(x) it only fits the bigger amplitude i.e. ignoring the small peak. If any body has any idea how to fit f(x) by taking the whole data.
Thanks