I am another one who wishes that I was diagnosed earlier. I am 44 and was diagnosed in September 2013.

A good book which you can probably get from the library is "BPD for Dummies". When I was first diagnosed I couldn't concentrate on reading much and it was very helpful.

DBT will be a big help. I am a couple of months into DBT and have seen a huge improvement. A good website is DBT Self Help