Late period, negative test results?

Off of birth control over a year, have been actively TTC (for the first time) for the past 3 months. Got a positive LH surge on day 15...on day 35 now with no sign of a period and several negative pregnancy tests. Doc is recommending waiting a week and re- testing... anyone have a similar experience and end up being pregnant? Trying not to let myself, but starting to feel discouraged :/