QueenIria it's not abnormal for speeds to fluctuate. If you look at your uploads, you'll notice one will for a period of time use much of the speed, but then for a period it swaps over to another upload which gets much of the speed, & so on. Major fluctuations I'm not sure, ... perhaps a collation of the same fluctuations from multiple sources. Just a guess.
Not sure if this will help but there's some tips here that do work:
To continue files downlding (click on link) I constantly use these techniques such as browsing & dc, etc. or cancelling the downld & reselecting from the search results. And doing fresh searches if needed.
(Another point is to vary the material you have to share b/c that attracts different people who may help you find new sources & harder to get files.)