Hi so I had sex like 3weeks ago. We use condom & everything. I don't think it broke cause I took it off of him but anyway I had sex with him like 3-4 days before my period starts & now I didn't get my period, I'm 15 days late, I took a test but it expires last year December but the test came out negative. Should I believe it ? Is this suppose to happen when you have sex before your period ? I use to have irregular period but now it started coming every month. Help please