Suggest Treatment For Delayed Periods With Negative Pregnancy Test

Hi I have had the IUD for 2 years now and i havent got it checked. The doctors told me to feel for the strings and i havent been able to feel them at all. I have had my period on the regular every month but i havent had it in the past three months. I will admit i do have unprotected sex with my boyfriend. I took a dollar store pregnancy test abd it said negative. I have been very moody and very irritave. i drank 3 whine coolers yesterday and got very sick.i was just wondering if i could get an opinion.. anything will help!