Botox: Too much? Or am I sensitive?

Some patients will report a "heaviness" to the brow which resolves within a few weeks.  However the dropped brow suggests that too much may have been injected.  The product will wear off gradually over the next three months, so you should see slow but stable improvement in your symptoms.

it sounds like you have brow droop due to Botox. The good news is that it isn't permanent.
Factors that can make this more likely to happen are:
1. Botox being injected close to the brow
2. A higher number of units of Botos being injected
3. A personal tendency to droop.
Many of the patients who experience droop have the following characteristics:
1. Prolapse (drop) of the fat pad that starts off positioned under the brow in youth
2. An unconscious habit to lift the brows to get the fat pad off of the upper lid in order to improve the peripheral vision in the upward direction
3. A forehead that has grown very strong by being frequently used to lift prolapsed fat pads out of the visual field. Heavy forehead lines are often a tip off that a patient is over-using the forehead muscle to clear the upper visual field.
I have dealt with this challenging problems the following way:
1. Inject the Botox further up from the brow
2. Inject fewer units of Botox over the brow
3. Explaining to patients that they will have more residual forehead wrinkles if we do #1 and #2 to avoid droop.
4. For those patients in whom prolapse of the brow fat pad is playing a role, I suggest that they consider an off label use of Latisse to shrink their fat, a so called "chemical blepharoplasty". After a couple months of use, we can often be a little bit more aggressive in treating the forehead lines because, although the droop will still occur, it doesn't impinge on the upper eye as much and so is not as cosmetically objectionable.
Best of luck to you.