I Have Extremely Irregular Periods And Always Have. This Time

I have extremely irregular periods and always have. This time I have missed 2 periods and had some spotting a few days ago. Around the same time, I started having severe lower back pain which has not gone away. It is also kind of painful to urinate. I have been drinking cranberry juice in case it is a uti, but was unsure if this might be a sign of pregnancy?