It's very hard to use H or any other pu mu agonist opiate and take suboxone at the same time. Suboxone is a partial agonist, which means that it binds to the opiate receptor in the brain but only exerts a partial effect (think of it as opening a door halfway) but binds very tightly to the receptor, making it difficult for other opiates to bind to the receptor, including H.
Suboxone has a much longer half-life than H, oxy, morphine, etc. Therefore, if you shoot H while suboxone is still active (~36 hs) you won't feel any effect. More imporantly, if you take suboxone while H is still active,, you will go into a precipitated withdrawal because suboxone will kick H off the receptor and reverse its effects.
Like you, I tried to use suboxone during the week when I had to hold my shit together for work, etc. and would try to use H, morphine, etc. at other times. Didn't work. Either I felt nothing or ended up very sick. Very, very sick.