Making me feel drugged.

I've been injecting sema for about two months. I raised my dose about a month ago and for the last three weeks I've been feeling super sleepy from about 8:30 AM to 11 AM. I can't do any work because I feel almost drugged. I've done nothing else different. I eat the same, sleep well, and take my usual medications. My doctor just told me to stop the sema for 3 weeks and see what happens. Has anyone else experienced anything like this?