I Got My Periods On 9th Feb I Have Tried

I got my periods on 9th feb i have tried to concive that month and expected that I could be pregnant coz i missed my periods. however got periods almost after 5 weeks plus i.e on 19th Mar. This month also i missed periods and its almot 5 weeks now. Can't fimd any common symptoms but having sore brest this month and pain in lower back and abdomen. Got negative home pregnancy test. Pls suggest.