I got my chimney swept 6 months ago why do I need another one already?

Creosote accumulation depends on many different factors. Typically, is it the moisture of the wood. If you are burning un seasoned or damp, wood it will make the flue build up with sticky black creosote very quickly. Wood with 15-20% moisture content is going to be the best fuel for your chimney as it won’t create as much creosote.