Pregnancy scare

I had missed my shot back in February. I never forget to get it but was in the process of moving out of state. I had a period right after my missed shot and now I haven't had a period for two months now. I did take a pregnancy test but it was negative. Now it's the month of May and still no period. Lately I've been experiencing slightly sore nipples What should I do? Should I take another test or visit a doctor?