If you've taken it twice this week, well three times including now, you certainly have a tolerance. By no means is it substantial, but you will definitely be able to feel how your tolerance has grown. I'd say you have a low tolerance for the doses you've been taking. 15-30mg over 12 hours which is realllllly not that much. 30mg Morphine ER comes out to 2.5mg/hour which is not much at all.
With every dose you take, you will notice the effect of tolerance more and more. Tomorrow when you take 45mg ER, you'll get 3.75mg/hour.
That being said, you should be careful because after you take the 45mg, it probably won't feel very strong right away, but it will keep building on itself every hour, so don't take a fourth pill and go to 60mg, because 5mg/hour is a substantial increase from what you're used to.
Tolerance to opioids builds extremely quick, and takes a loooooooong time to go down. I would say more than months. Going months without and then dosing will certainly be much stronger than it would taking it daily, but by no means will it ever feel like the first times you did opioids.