Color causing hair breakage?? HELP!!

Hello.  I hope someone in this forum can help.  My natural hair color is very dark brown, almost black.  For the past year and a half, I've had my hair blonde.  I absolutely love it.  A few months ago, the stylist I'd been with through the entire transformation moved out of state, and I had to find a new one.  I did, and I think she did a pretty good job of matching the color up.  I've had 3 visits with her so far (every 4 weeks).  I need to go so often because my natural color is so dark.  Anyway, here is the problem.......I'm noticing a bunch of things with my hair........It's shorter, and I did NOT get a hair cut in the past 3 months.  It's thinner looking.  It's not styling the way it used to because there is less of it.  I'm kind of freaking out, because I don't know what to do.  I love the blonde, and do not want to go back to dark brown.  I didn't have this problem with the other stylist.  Can anyone provide any insight.  I only changed one thing on my end.  My diffuser broke a couple months ago, and I couldn't find a new one.  When my hair came out the same way as it did without the diffuser, I didn't bother to purchase one.  Could that be a factor in all of this?

Thank you in advance for your reply.  Please HELP!!!

How do you take care of your hair? What do you use on it? Does your stylist use heat? Do you use a flat iron? Some of this stuff could be a contributing factor. The blonde hair needs tender loving care. I've been bleaching blonde for about seven years and haven't had any major problems. I had a bit of breakage at one time but I came back from that quite quickly. A diffuser probably is better than a regular dryer since the heat is, well, diffused whereas the regular blowdryer concentrates heat in one spot only. 

What kind of hair do you have? Some kinds are more delicate than others. Though I have fine, myself, and it handles it ok ...