Could this be anemia?

If there are no other underlying diseases, then yes it could be a type of anemia. I would suggest increasing your iron intake. Red meats ,dark green leafy veggies and iron supplements taken with something acidic to increase absorption. Being on your period won't help your anemia, because you are losing blood and can actually increase the effects of anemia. If it doesn't resolve after a couple days you should get a thorough check up and maybe some blood work. Also it could be scurvy if you haven't eaten or drank something with vitamin c for an extended period of time.