no period yet..?

So I took plan b just because I was paranoid (my first time, no condom for a few moments but he never came) around Jan 15. I got a light period a couple weeks later, then had a full period a couple weeks after that. Now the app says I was due for my next period a couple days ago.. and it's still not here. I haven't had sex in three weeks and I've always had protected sex save for two times (neither time he came close to ejaculation). Should I be worried? I feel like I'm having PMS (moodiness, crying, depression, tiny uterine cramps, tiny headaches, and stress)