Receiding gums or weakening enamel?

I hardly ever go to the dentist, but I haven't had a cavity in about 15 years. I would say I take pretty good care of my teeth. I went to the dentist last probably 4 years ago, because my tooth was feeling sensititve, and it turned out I was brushing too hard. Well a few months ago, I started feeling sensititvity, and started scratching at one of my back molars, and felt a ridge about 1/4 of the way down from the gum line. It feels almost like a straight line, and only goes across the front. It is a bit sensitive to cold. I was wondering if maybe it was enamel loss, or receiding gums. I believe I was brushing too hard. I have gotten a soft bristle brush, and was wondering if anyone had suggestions. I am trying to avoid the dentist, because I have no insurance, and don't make much money as it is. Any thoughts?

Receiding gums or weakening enamel?
It sounds like your gum has receeded to expose the interface between the enamel and cementum [root surface]. This gum recession can be caused by gum disease [highly probable if you haven't seen a dentist in a long time],or by brushing too hard,or by grinding your teeth. I exposed my molar root surfaces by over brushing and not having a dentist do regular cleans and my dentist desensitized the teeth by giving me some tooth mousse and desensitizing tooth paste. I started using an electric tooth brush properly ie brushing gum to tooth and by flossing and in a couple of severe sites they had to do a gum graft.

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