I am glad that you are taking the advice seriously. You are at the age where this type of mental illness tends to appear or get worst. It is possible that this is the only the beginning of your anxiety. The good news is that there are treatment options that can help. It can be a slow process but it can be treated with success.
If you do a web search, you will be shocked at how common excessive anxiety is. You will also likely be amazed at how many of your fellow students you will see at the counselling center who are seeking help for various issues. You are not alone or even unique in needing some professional help. Do not hesitate to discuss these issues with a professional.
Many people will feel or tell you that this is a simple mind over matter issue. That you just need to confront your fears and get over it. If you have a actual mental illness, it is not that simple. A professional can do a evaluation to determine what the issues are and discuss your treatment options.
Noname87 has provided some very good advice. You have to get the problem diagnosis first then you can work on the cure. There are many folks who feel the same way as you but are afraid to say something. You admitting there is a problem is a huge step and you may have help someone else here without knowing it. Best wishes to you.
Oh for goodness sakes! I wasn’t suggesting the OP hide under the bed. All deBecker says is that you should pay attention to your gut instincts. Someone makes you uncomfortable? Don’t go into the dark alleyway with them.
None of us saw “creepy guy.” There might be something real there, there may not. In any event, the fact that she says she can’t focus on anything else for fear of this sounds like counseling is a good idea. But don’t invalidate her instincts, which may be perfectly sound even if she’s overreacting in this particular case.
I agree about instincts vs. over-reacting…my mother is what used to be called a “worry wart”. She get anxious about every little thing and is always worried about this thing or that thing happening. There are degrees to everything and even with my worry wart mom, i would say the things she worries about generally have some modicum of validity and it makes ‘us kids’ roll our eyes but it does not prevent her from being functional - counseling can possibly help the OP learn how to keep her worrying and anxiety from becoming debilitating or cause dysfunction.
stradmom, you’re missing the point.
Those of us with high anxiety ALWAYS have guts that say “FEAR THIS! FEAR EVERYTHING!” If we listened to our gut all the time, we would not get out of the house.
I understand stradmom’s point but also definitely with romanigypseyes. It’s hard to distinguish between actual instinct and just crumbling anxiety. 
That’s what mental health services are for 
It sometimes takes years but most of the time we can learn to distinguish between what situations do and don’t require fear and anxiety.