Cycle length fluctuating

Hi ladies! My husband and I have a son and our TTC for baby #2. I stopped taking my birth control in February and since then my period has been wacky. I go from a 28 day cycle one month, 35 the next, 29 the next, and now I am on day 33. Still no period on day 33 and have taken two negative pregnancy tests. I am becoming very frustrated. Should I call my doctor?