Toprol-XL and struggle

I do not feel horrible but Im starting to experience a sort of constipation. I'll go a day and a half struggling to produce a bowel movement. Then finally I get a satisfying result. It's a struggle though. I push and push and push. I've been on 50 mgs for three months. I have to refill today. I will mention this to pharmacist. My appointment is not till the end of September.

I am on 200 mg of Toprol, because I have cardiomyopathy. In about 2001 I was feeling very poorly, fighting and gasping for breath whenever I lay down or adjusted my position in bed. I had been advised that with my height and weight I could expect to be able to tolerate not more than 150 mg of Toprol. By this time I was in assisted care. My regular doctor was out of town, so I asked another doctor in our clinic if my dosage could be adjusted back to 150 mg. This doctor agreed to this, and I immediately felt noticeably better. Shortly after this I was out of assisted care and back in independent living. I continued taking 150 mg for the past 5 years.
But I recently changed doctors, so that all my medical records could be with the same system. The new doctors have raised my dosage of Toprol up to 200 mg, and I have been experiencing some of the same symptoms I suffered in 2001: Exhaustion, great weakness, episodes of fighting for breath several times a night; at times I sense that the struggle may not be far from death!
The doctors say I now have to be on maximum doses of drugs. But I do not smoke or drink, and sense that people like us sometimes need smaller doses than others. Out of desperation I have just started reducing my own dosage back to 300 mg in two days (150 a day). The pills are almost impossible to split, though I can break them in half, so I am taking 200 one day, 100 the next. Last evening I took my first 100--and slept through the night WITH NO BREATHING EPISODES!
I'm going to make notes on my daily results and inform my doctors on what I find.

taking metprolol for high bp since last fall (slmost one year).
It has decreased my ability to coordinate my movements--I am clumsier. I have gained 12 pounds, and find that my weight has become a real struggle, in spite of much exercise and activity. I am depressed, and my short-trem memory is impaired. I learn new information only with great difficulty.
Sometimes, lately, I have transient moments of aphasia.
I guess its time to see my Dr. and change meds, because this beta blocker Rx is really hurting my quality of life.