I was in a similar situation to you with being concerned about people knowing. I lost the majority of my hair (on top) right out of high school. No one ever mentioned it to me but I eventually noticed my hair would grow to a certain length and stop. I did the shaved head thing for awhile and liked it, but it made me look much older.
I looked at the surgery options and they're just too expensive for such a thin density result. I eventually learned that we had an Apollo hair center close by and I eventually became one of their clients. I had no idea that you could do hair replacement online so I believed every word they said. They gave decent results but the cost was too high.
I left work on a Monday with the typical horseshoe hair that the majority of men have and returned on Saturday with a head full of hair that looked great. Some people noticed and some didn't. The ones that noticed were of course bald and only brought it up because they were envious. If anyone asked what I did, I told them. If they liked it that was fine and if they didn't that was okay too. People get LASIK eye surgery, breast implants, liposuction, Botox, nose reductions......
People do these things to feel better about themselves and be more confident. If it makes you feel better others' opinions shouldn't make decisions for you. The point is, the sooner you do this and see how much better you look, you won't worry about what others think.
Sid