WASHINGTON — Three years ago, Jason Prosser was stunned to discover the cost of child care for his newborn son — so much so that he and his wife postponed having a second child.The day care center they found near their Seattle home tops $10,000 a year. Next year, their son, now 3, can attend a Catholic preschool less than half as costly. “It’ll be nice to have enough relief next year,” Prosser said. “It’s just funny that the relief will be a private school.”He and his wife are among legions of middle-class families who are straining under the weight of accelerating costs for a range of essential services from day care to health care. And now a study by the Center for American Progress shows just how heavy the burden has grown: For a typical married couple with two children, the combined cost of child care, housing, health care and savings for college and retirement jumped 32 percent from 2000 to 2012 — and that’s after adjusting for inflation. Compounding the pain is that average pay for Americans is barely topping inflation. The figures help explain why many Americans feel stressed even as the economy has strengthened — and why some feel bewildered to hear that overall inflation in the United States is, if anything, too low.