How many points did you have to agree to pay? Does your credit score get you the best rates? How much are you putting down? All these factors affect your rate.
For excellent credit, 25 percent down or 25 percent minimum equity for a refinance, and a 30 day rate lock, my local credit union as of this evening is quoting 4.25 percent with zero points, 4.125 with one point, and 4.00 with two points on a 30 year fixed rate conforming mortgage.
This lender locked your rate and unless there is an agreement to relock if rates go down, that's the deal. You could start over with another lender, but you might lose the house if you are trying to buy because the loan can't close on time.