Late on my period

Stopped taking birth control 2 months ago, had a period February the 24th, we're now March 25th and I still haven't came on. Me and my partner had unprotected sex during the month. This week I've had very sore nipples and boobs and they're heavy and all of a sudden became veiny. Could it be that my old contraception is messing up my cycle or could I actually be pregnant. I took a test a week ago which was negative, when do I take a take a pregnancy test after missed period?