In past I had some obsession with taharah but I noticed one thing during my problem. I was obsessed with purifying my body but not obsessed with purifying my soul. Why is it that people (including me) become so careful for physical taharah but are not so careful about taharah of the soul (i.e. staying away from sins)? I understand that shaytaan(LA) is the driving force behind the obsession with physical taharah. But is there any psychological aspect to it as well?

Yes it could be related to OCD. This requires treatment some times