I am going through the very SAME thing... and have been for several months.
I had breakage in the SAME section of my hair last year and I am STILL in the process of growing it back.
I was able to get my hair cut in a style that camoflauges the breakage and can also wear my it back, but I found myself trimming on several occasions because I have been uncomfortable with the appearance of my ends. I haven't started making progress until recently because I only started assessing the problem in March.
erplexed Based on my experience, I'd suggest that you:
1. Think about what makes you comfortable. If thickness is more important to you than length, trimming would be a good option. If you want to retain length, try finding styles that will allow you to maintain your length without showcasing hair thinness. Basically, you have to do what makes you feel best about your hair.
Since it sounds like you aren't happy with your hair looking so thin, a trim might be a good idea.
2. Determine why your hair looks thin. Do some sections of your hair grow slower than others? Do you have breakage? If fullness is your concern, and you aren't concerned about length, cutting your hair is the best way for it to look thicker in the short-term. If that section of your hair grows slower, be prepared to wear shorter styles for a long time while it "catches up" with the rest of your hair. If breakage is the culprit, make sure you address the underlying issue so that you won't have to deal with the same problem in the future. In my case, the hair that broke off was coarser and drier than the rest of my hair so I FINALLY
realized that I had to moisturize it more frequently and manipulate it more gently when I got close to the time to get a touch up. As luck would have it
this area also grows more slowly, so I started taking a supplements to speed up my growth. I seem to be making progress
but I just wish I could have starting seriously working on this sooner.
Best of luck!