Should I tell my bf yet

I haven't gotten my period and I'm worried that I'm pregnant. I'm seven (or six)days late and maybe it's nothing, it could be stress messing with my cycle because that's possible. I took one of those cheap pregnancy tests and i got a negative but i still haven't gotten my period. What worries me is that I got three false negatives while I was pregnant my first time and didn't get a positive until I was around three months. Like I said it could be that my period is just really late but I'm not sure if I should tell my boyfriend that I could be pregnant or if I should wait longer until I knew for sure, but if I am pregnant it would probably take a while for me to get any results like it did the first time. The uncertainty is driving me a bit insane 
I also using 3 period tracking app lol 2/3 are saying I'm seven days late and the last one is saying six and I checked and since February my cycle has always been 36 days until now