Could Sore Breasts And Tiredness With Delayed Periods Be Due To Stress?

My husband had a vasectomy 4-5 months ago & we had unprotected sex on the 26th day of my cycle - did not think I was ovulating although he has not yet had his sperm levels checked (he has however ejaculated 20+ times). My period is late by 4 days now - I am on day 37 of my cycle! Sore breasts, vaginal discharge (clear & at times yellow), crampy, tired, emotional, etc...I have had 3 negative pregnancy tests? Is it PMS, stress, or could I be pregnant?