What Causes Sore Nipples, Lower Back Pain And Cramps?

hi im 24 and for the last 2 weeks my nipples have been so sore and i also have been having lower back pain. me and my boyfriend use the pullout method. he also have been sleeping a lot lately. my period is suppose to come on today but i have been getting lower abdominal pain for about a week and have been getting nausea lately. can this be a sign of pregnancy