Can Steroid And Stress Cause Irregular Menstrual Cycle?

I was supposed to get my period at the end of January/beginning of February. I was prescribed steroids in late January and got off of them February 7th. I still have not received my period. My last period started on December 31st and ended on January 6th. I have had sex, but used condoms. I have taken 2 pregnancy tests. Both were negative. I took one on Feb. 9th and Feb. 16th. I have had signs of pmsing, but have not bled at all. I haven t really had any signs of pregnancy besides the missed period. Is it possible for the steroids (and stress) to make my period this delayed? And do I really need to take another pregnancy test even though two were negative?