DO you have lab results? What does the doctor consider "normal".
When you take Cytomel only, your T4 level goes low while your TSH stays up. When you take T4 only, your T4 levels goes up, but your T3 tends to stay fairly constant in most cases, since T4 is converted to T3 in the liver.
Most tissues need T3 since it is more active. Some tissues NEED T4 because they don't absorb T3 well. The brain is one such organ that NEEDS T4.
I would bet that a dose increase on the T4 med would have helped you. 75mcg is a fairly small dose. The addition of a little Cytomel (5-10mcg) may have helped, too, but I think it should have been in addition to the T4 med rather than in the place of it.
There are cases that are exceptions to what I just wrote, but they are few and far between.
I am not a doctor, nor have I ever played one on TV...