Am I pregnant ?

TTC for 6 months with my hubby bear and it's been a rough and to be honest stressful journey . There has been two to three times we've thought to be pregnant but when I tested it was negative . I'm currently 5 days late and I waited til yesterday which was the fourth day to test and it was negative. My husband calls me every hour to see if I started my cycle and I'm just trying to not be stressed or disappointed about it . What do you ladies think this could be ? 
FYI I used a cheap pregnancy test , all my friends suggested it and said it worked for them . Could that be a factor as well ? Thank you so much