Imuran therapeutic range question

Hi, I made some posts before maybe you'd remember. Here is a qucik summary;
Was a long term pred user, added Imuran with 100 mg dose on May 17th, increased to 150 mg(I weigh 66 kg) after two months and started tapering pred in the meantime. I was suffering from long term pred side effects that had become really disturbing for me. Tapered down to zero around week ago or so.

Current meds; Salofalk 500 mg tablets x4, Imuran 150 mg

Results; got a bit worse compared to my time on both Imuran and Pred but my condition seems manageble, no pain, my poo doesn't seem to be solid most of the time but blood seems mostly absent. Even when it is present it's like drop at most which is better compared to my time on pred only. Urgency seems to be also absent but I'm mostly at home with a toilet near me so I haven't "tested it" for longer durations. Didn't seem to bother me during the few times I stayed outside though. I go around 3-4 times a day with the first two being in morning and very close to each other. Hope it stays like this during the fall & winter.

My only complaint is that kinda get incredibly sleepy from time to time and sometimes when that happens I somehow can't sleep when I throw myself into bed. Wonder if there is anything I can do to counteract that, pred felt like it was kinda doing exactly that.

So, I'm on my 15th week on Imuran. Almost 4 months in. I'm guessing it started showing effect since I never felt this good without pred. Can I still get better with these meds? Does the initial effect get more powerful as time passes?

Hi again iPoop.
I asked around for the Thiopurine Metabolite test before, my sister who works in a small town hospital told me they looked it up and it's not a test that can be done everywhere. After that, I asked for the test in a big university hospital here, in internal medicine policlinic and they told me they never even heard about it. I'll travel to see my own doctor in a week or so to see if he can get it done. He'll probably take a quick look at my colon too, he does it everytime without any kind of scheduling.

I did CBC and LFT tests around a month ago. Only thing out of range was iron levels everything else was fine; liver enzymes, rbc, wbc, platelets, you name it. I'll ask for them again though.

The reason I ask about whether I can get better or not just with imuran is, I was better on pred. Solid stool was indeed an achivable dream with it. I'm just kinda afraid I'd have to take it again. Otherwise I'm actually happy with the results I'm getting.

I'm in Turkey.