activity levels?

This may seem kinda stupid, but I don't quite understand the activity levels under account settings. Like I have it set for moderately active, because I jog for about 30 minutes 5 times a week. I also horseback ride for about 30 minutes 4 times a week. But I go to school and sit around all day. And I don't necessarily go home and do heavy housework either. Moderately active says all three of these things. Does that mean I have to exercise most days, have a hard job, and do heavy housework to be considered moderately active? Or do I just need one of those, such as working out 5 times a week?

If you're at school (under 21?) the CC calculator isn't calibrated for people your age.   This site is much more accurate..... http://www.bcm.edu/cnrc/bodycomp/bmiz2.html

Enter your age and current stats and, in your case, read off the Daily Energy Requirement for 'moderate activity' because you'll be getting an average of about an hour of activity a day..... 30 minutes jogging, 30 minutes horseriding and presumably you walk around between lessons and do other things that aren't purely 'sitting down'.   I don't know how old you are (15? 16? 17?) but it looks as though you need about 2100 cals a day as a starting point. 

The most common reasons for periods stopping are.....

• Being too low a weight  - and even if your BMI is technically 'healthy' that doesn't mean it's the right weight for your body to be healthy.  (Ironically, 115-120lbs was a perfectly healthy weight for you and you may need to get back there before you recover.)
• Too low body-fat %
• Excessive exercising
• Poor diet..... especially one that is low in energy (calories) and fats

If you haven't had a period for more than three months you should see your doctor.  And in the meantime, I think you need to be looking at 2100+ cals a day and including plenty of fats in the mix.   If you gain weight as a result, that's probably a good thing.