The problem is certainly that Feedly only visits your feed one's a day (wich is quite surprising), so you only get the 3 last items.
To avoid this (and without coding) you could try to build an IFTTT recipe from your RSS feed (Feed channel in IFTTT) and publish it to Blogger (Blogger channel in IFTTT). The feed of Blogger have a 20 items "depth", wich would fit the rhythm of Feedly. Let's hope that IFTTT scraps the feed several times a day.
You'll subscribe this feed in Feedly.
Note that Inoreader offers a feature where you can "boost" the feed scraping frequency.
Could you share the URL of this feed with us to consider other solutions?