Let me get this straight....Your 1st bm of the day is really bloody and subsequent bms have less blood if you don't take the suppository. If you do take the meds, your bms are less bloody from the start. And your question is why?
If this is indeed your question, and I am understand you correctly, keep reading. if not ignore the rest.
Your first BM will usually be the bloodiest because you have been "saving up" all night long. Once you expell that, your subsequent BMs will be less bloody. While on the meds, the reduction in blood is due to the meds working on healing your colon. If you were to continure on the meds, I suspect your would have less and less blood every day until you have none. (At least that is what happens with me). The suppositories (I have never used) don't reach as high up as the enemas, and if your disease is reaching higher up, you should consider taking the enemas or cortifoam. Hope this helps.