Silhouette infusion sers

I have been using Silhouette 17mml cannula infusion sets for about 4 months. I was having good results with them. I had only a few that were not successful. Just recently about 2 weeks ago I my sets were only going for 2 days where as before they would go the full 3 days. The cannula seems to leave my skin with a big red dot. I was wondering if I switched to the 90 degree sets I would have better luck. I was on the Mio advance before but I was getting sites in a blood vessel and then my sugars would go high. What do you suggest?