How to know she is pregnant or not?

On 6th march we had protected sex but comdom was upside down...And flipped and had sex...Next day she had ipill and on 15th march she started bleeding like periods and it last upto 19th march...And we had sex on 18th march and 19th march after that she had once again bleeding like periods on 24th-25th march...As her cycle was of nearly 22nd date of each month...After that we had sex on 13th,14th,15th april 7 times...But all were protective and no semen had gone inside vagina but she started breast tenderness, abdominal pain, headache on 20th april...And today she had taken pregnancy test and is negative... only "C" band is coloured ...But there is no period until... whats the reason of that is she pregnant or not...?? Sir/mam plzz help me... Whats the problem why theres not period or is the sign of pregnancy?..