This is extremely common at this stage in life. I'd be shocked -SHOCKED- if there weren't a counseling center on campus. The pressure of school isn't really that bad, it's the pressure of post-school that did me in during those years. I haven't really recovered. I wish I had been sound enough to recognize how much help my local campus counseling might have been.

As for explaining your sitch to your family and friends, I often find that the best approach is to be as honest and direct as possible. Don't fake it being better than it is to make it less uncomfortable. Be earnest and forthright, and hopefully at least one of them will clue in. Also recommended is printing out any threads you write in on here and giving it to them. It's sometimes easier to express yourself with total strangers like us, and then it's just a quick hop to giving the printout to the loved ones.

Take care, and welcome!