I don't know where I'm going wrong with my dose

I was prescribed suboxone in February to come off a severe oxy and kratom habit. I'm prescribed two 8mg subs per day. I started on the films but recently switched to the tablets and actually prefer them. That being said.... I dont understand what's going on with my doses. Sometimes they work great and I feel great for a while. Other times its like I feel no effect from them whatsoever. When I do actually feel effects from them it takes 2 to 3 hours for me to feel anything or any relief. Where am I going wrong?