All of those suggestions are good WillowSheaCurls! I know some people have some success massaging Jamaican black castor oil into that area of the scalp. ALSO, I have noticed that I also have some thin edges partly from chemical damage in the past. That seems to have taken a few years to get better, so be patient if that is the case for you. Another thing is that, your natural hairline might just include a lot of baby hair. That is what it sounds like to me since your edges are both thin and soft (sounds like baby hair, or normal edge hair). Don't lose hope or get frustrated if nothing seems to help since this too might be the case.
I agree - castor oil! It definitely takes time though...the results won't be instant. Chescalocs on Youtube made a video documenting her progress growing her edges with castor oil for a year >> http://youtu.be/dyWhZysuPWM