I'm late but irregular.... help

Okay so sorry if it's too much information but I'm irregular. Sometimes it'll be about 3 months the latest for me to get my period. Recently, I've been getting it every month since January. Not in an expected date but I would get it every month. I know when I'm about to get it too because my back immediately starts to hurt. This month around the end I started getting terrible cramps and backaches but still no period whatsoever.... should I consider buying a pregnancy test or? I'm scared to get a pregnancy test at the same time because then I get hopeful and for it to just tell me negative kind of makes me upset.... any advice? is anyone else going through this?