If you're still using your toothbrush until it gets like that, are you sure that your gums are okay? 0w0)??? I believe you only need to brush well the surface area of your teeth. It might hurt if you put too much strength on it and it gets all frazzled like that. For hard-to-reach nooks and crannies or food remains that are stuck on them, just use toothpicks and dental floss. A toothbrush would only look that way for me after I used it for cleaning tiles or scrubbing the kitchen sink (which are things I save my used toothbrushes for). I replace them every 2 months, which is the same timing for the replacement of my water filter and checking the air conditioner filters too, so it's all done on the same day.
It will probably take years before my toothbrush look like that. I brush my teeth 2x a day but all my toothbrushes never looked like that ever since. I change my toothbrush once every 3-4 months to be hygienic tho.