Why is my hair so tangly and dry?

After I shower lately my hair has been extremely tangly and dryed out. I am trying to grow my hair longer and I dont want to damage it by having to comb through all these tangles. The strange thing is is that I haven’t changed my hair routine except for I have been doing hot oil treatments and deep conditioning my hair. I have even stopped straightening it! Does anyone know why my hair is so dry despite all the good I’ve been doing to it? And what do I do to fix this problem?