A little unsure about where to start ...

Hey guys! I've been an MFP regular for quite some time (I quit using my old account and started using this one recently). When I started logging I weighed 209 pounds and 5'5"(5'4" and 3/4s of an inch if we want to be technical) and I was unhappy. I was using the 'Special K' diet initially because I didn't really know what to do on my own and I needed some structure to build my diet on. This was in July of 2013.

Flash forward to now. My weight is fluctuating between 135-140 lbs depending, and I work out for an hour 60-70 minutes 5 times a week. I have been eating under 1200 calories (not including the extra calories I expend when I'm at the gym) because I've been pretty determined to keep the weight off ... I'm probably not reporting my eating habits as accurately as I could be from time to time, but I try to over-estimate when I'm logging on here ... my weight hasn't gone down in quite sometime (actually, it is on the upward scale now). But ... I'm kind of worried about myself ... I feel reasonably ok, but (TMI) my period stopped in April and hasn't returned . I've never had a very reliable monthly schedule, but it has been away longer than usual and I should definitely still be having it, since I'm still youngish and am definitely not pregnant. In addition, I've been feeling dizzy and nauseous.

Judging from posts I've read on here, I've kind of come to terms with the fact that I probably should be eating more calories ... but to be honest, I'm not sure where to start without binging and ruining all the progress losing the weight I've made. Any suggestions? I think I have a pretty restrictive diet ... I eat a lot of fruits and veggies and low fat/nonfat greek yogurt but I don't eat meat often (actually, I don't eat beef/pork at all), and bread, and protein bars.