My periods got delay for 2 week. Previous month bleeds for 2 days only & now 3-4 drops only since 3 days. Previous month my boyfriend ejaculate externally... is there any chances of pregnancy ? And after 1week I have tested for pregnancy, it was negative. Is there any problem ?

If you don't want to be pregnant there could be a problem. There is always a chance of pregnancy when having sex, protected or not. A missed period is the best indication of pregnancy.

Doing, outside, still gives lots of sperm for pregnancy, what other, if there was, birth control was used.

But wait one more week, test first thing in the morning , with first urine of the day