I had sex for the first time March 15th, and took Plan B the very next day

Ok so I had sex for the first time March 15th, and took Plan B the very next day.  Got my period a week later, so no big deal.  Then about April 15 my bf and i were going to have sex again since my period wasnt due for a few days, but right when we started, the condom broke and so we stopped.  I didnt take plan B because the condom has spermicide in it, and we didnt even do anything, he just stuck it in and it broke.  Problem is, I havent had my period since the one back in March, and i am seriously freaking out.  People say that Plan B can throw off your period cycle, but can it this much??  Also, i have smoked weed a couple of times this last 2 months, and i was told that that can also have an effect on your cycle.  Sorry this is so long, but im scared and need some help figuring this sh*t out! :/