Late but scared to test

I'm 4 almost 5days late for AF and I'm scared to test after trying and trying and continuing to get negative readings I'm honestly getting discouraged. My doctor only gave me two years to conceive and have the baby before I'd have to start treatment for my cancer. I'm so scared I won't have a chance to be a mother. I'm so nervous every time I go to the bathroom or when I wake up in the morning that I'm going to see blood. I want to test but am so scared of being let down again. I don't know what to do :( Should I test now or wait longer? My period was four days late last month with no normal symptoms of it coming same this month. I've been going to the bathroom more frequently, vomiting, my nipples are slightly darker and breasts are softer and hurt, I also have terrible heartburn. I don't know if my mind is playing tricks on me or if I am actually pregnant :(