Heya Lise.
I had the same problem.
Do you use any leave-on conditioner on your hair after the blow dry? You need to because it will moisturize the hair.
As well, I find that switching shampoos and conditioners weekly works. I have about 3-4 brands that I switch. I've noticed drastic changes since I have switched last year. Buy salon products. The brands I really like and use are: Nioxin, Paul Mitchel (his line of green tea is nice), Redkin, Abba and Neutrogena.
Neutrogena has a deep-cleanse cleaning shampoo that you would only use once a week to take away the residue and bad stuff from your scalp. I use this quite about 3 times a month along with their conditioner.
There are other tips that I've read but the one that I really love and really works is leaving in malt vinegar. You put half cup malt vinegar with half water. Leave this in after you have conditioned your hair. Do this for a month and your hair will be gorgeous.
You could substitute with beer, mayonaise... but I haven't tried this before.
Hope this helps you Lise and good luck.