Should I see a doctor? (pregnancy vs pms)

No period this month. I am now on day 50 of my cycle. I took a test on day 40, and it was negative. Since I have days where I experience what feels like my period coming, then nothing. I've been experiencing this faux period paid since, like, day 28 of my cycle. I also have been getting intense lower pack pain, and my nipples have been extremely sore for the last 4 days. Still no period. Should I go to the doctor and get a blood test?