rollin420girl, lots of things can screw with your period, especially stress. I have only tried jwh-018 once and in its powder form, so I haven't much experience with the synthetics (I'm one of those people that go into those threads and says "JUST SMOKE POT!"). There are a few other factors, though, which can help explain the missing period:
You're a virgin, so I'm guessing you're young. Are you regular, and get your period at about the same time each month? How long have you been menstruating for? Have there been times in the past where your period just didn't come, and skipped a month or two? I'm pretty regular, but in the 12 years or so I've dealt with this, there was a small handful of times where it skipped a month here or there. I'm assuming you aren't on birth control either (I have been since I was a virgin for menstrual issues so it's always possible, not a virgin anymore but have never been pregnant). These factors may have something to do with the skipped period.
However, sega and drscience are absolutely right --- no one has any clue what the side effects of these synthetic chemicals are, so there's no way to really know if Spice is contributing to it. I know opiates stop some women's periods, theres a few threads about it on BL, but I'm not sure that it's a common drug side effect unless theres a big change in weight, or its something speedy which puts a lot of stress on the body.