Ah this is happening to me right now! Since snot traps the dust and dirt that you inhale and form a booger, you're probably getting them more because you're more exposed to dust and other airborne particles than before. This could be because of fall as well - first of all if you live in the Midwest, or somewhere else seasonally humid, this time of year it starts getting drier, and even your nostrils aren't as moist as usual. Also, now is the time of year when farmers begin harvesting, and the harvest throws more particles into the air than there normally are. I live in the Midwest, so the humidity affects me, as does the harvest (I am surrounded by crop fields), and I just started college. My dorm room is older and very dusty, so that also has an effect. ANYway, look for sources of anything like this and you may just figure out what's going on.
Hope this helped [: