ladies I need help

So I have not gotten my period in 4 weeks, I been having unprotected sex for the last 3 months and I took a pregnancy test last week and it came out negative. I always been irregular but for the last 4 months I been getting my period around the same days. What can I do to get my period? We been having unprotected sex this whole month because My husband wants me to get pregnant but how can I if I don't get my period.