I too have just been recently diagnosed and it was quite the surprise. I had no obvious symptoms and I too found out through routine blood work. My TSH was at 5.125 (normal range being 0.450 - 4.50). So, I am only a little hypo, but it is there. I am only 26 years old! And from what I know, no one in my family has this, as it can be genetic. I eat healthy, I don't drink or smoke and I excercise regularly (honest!) I don't understand why I have this either. I have the most common type, which is Hashimoto's Thyroiditis. It is when your immune system produces antibodies that attack your thyroid tissue. It is unclear why the body does this.
My doctor said there wasn't anything I could do naturally to help it and that it will get worse (over time) if I don't do anything about it. I am not keen on taking pills, but I have discovered this is something I have to do. I started taking Levothyroxine two weeks ago and am NOW experiencing symptoms. I am pretty tired and I can't concentrate as well. I have read a lot about Levothyroxine and I am thinking about switching to Synthroid, being that I am early on in treatment and the switch shouldn't be noticeable.
Oops, sorry for making this so long
It feels good to know that I am not alone and to talk to others that are feeling the same way I do.