Hey girl. You don't have to start over!
Putting the hair up is not bad in and of itself. For some, bunning wet hair leads to breakage from the tension placed on the hair as it tries to dry/contract. Buns are still my main style, but I only bun my hair when it is nearly dry. Also, if your hair is a length where to bun it you really have to work & put tension on the hair to get it in the holder, I'd opt for other styles until you get a to comfortable bunning length. Also inspect your hair untensils. (ex: are combs seamless? gentle, non-nylon brushes? scarf protecting at night? watching the placement of hair pins/weaves?)
The health issue that led to your shedding may have alot to do with it, too. Not only does shedding remove the hairs that are hormonally scheduled to fall, but it can remove other healthy hairs around them by tangling with the good hair as it tries to fall. This can lead to breakage. So, make sure you are taking good care of your health and eating a balanced diet. A multivitamin may be beneficial as well. This will improve the quality of hair that your scalp pushes out. If your body is undernourished, your hair will be too and then you're gonna be working on keeping it fortified through external treatments. Its better to start off with hair that is inherently strong.
And nobody's hair grows blunt (well, at least I don't know anyone who does). Like the others have said, it may be differences growth patterns. If possible, try to do a visible inspection of the ends and length. (If your hair is not long enough for that, use shed hair.) If you see areas of weakness, damage, splitting, unnatural reddening, etc. you know that that hair needs to be trimmed. You can try to remedy the damage with treatments, but the effects are temporary. If your ends do look well upon inspection, you can hold on to them and trim once you've met your goal. However, if you let the hemline get too bad it may hurt you when you detangle, and you may end up losing hair to breakage that way. Combing through even hair is easy because the hair does not catch on itself or in other hairs. Each hair moves freely.
Also, the key to the regular dustings is to DUST. It is really not a conventional trim. Assuming an average growth rate of 1/4-1/2 inch per month, removing 1/4 or less every 6-8 weeks should result in a net gain.
Do you have any pics of your ends? It may not be as bad as you think girl. You know we are all our own worst critics.
Sorry so long!