Gosh, this is just very unwise. Plan B is not considered birth control. If you are going to continue to have unprotected sex, you really need to get on birth control or buy condoms and use them every time. You are playing Russian roulette. I wouldn't recommend you take plan B again this soon== your system is going to be a mess. The Plan B is a ton of hormones and they stay in your system for a while. As to pregnancy, that is also a timing issue of where you are at in your cycle. Your period will most likely be irregular for the next 3 or so months. Take a pregnancy test two weeks from the last unprotected sex you had to make sure it's not positive. But do consider getting some solid birth control under way so you don't have to have this situation which I'm sure causes you a lot of anxiety. good luck
Plan B is 89% effective for 72 hours. There's an 11% chance of pregnancy.