[The Lizard of Oz]

First, don't be anxious. You'll probably do fine whatever you decide to do, so why worry about it too much? In this context there can be wrong decisions -- like marrying a 35 year old feminist breast cancer survivor at 19 would be a wrong decision -- but there isn't such a thing as the right decision, so just choose one thing or another that seems promising and enjoy the ride.

Second, and this is an advice I would give only to someone who is in a serious STEM field and has some talent in that direction, consider grad school. In a field like math, there is really a lot more to learn than what you get from an undergrad degree, and getting an advanced degree will let you expand your opportunities down the line. And if you have the knack for it, it's one of the most enjoyable and productive skills to have that you can use for pretty much your whole life. Finally, if you stay in a college environment, are athletic and physically attractive and have even rudimentary game, you'll have your pick of young pussy. So it's something to consider.