I think I may have figured out the tired and stupid feelings. The day before I started the Avastin/Abraxane combo, I also stopped taking my antidepressant. I'd decided to taper down after being on sertraline since last July. It took about six weeks but I finally had the last dose last Saturday. A friend warned me that going from 12.5 mg to 0 mg would be harder than going from 25 mg to 12.5 mg, and boy was she right! So it's possible that my fatigue, insomnia, and feeling stupid is more related to stopping the sertraline than to starting the new chemo combo.
At any rate, having three evening activities in a row this week didn't help either. Somehow I got through everything (still feeling stupid) and plan to do practically nothing today. I will forego yoga so that I don't have to drive while feeling this way. Plus that will allow me to take a nap. I hear the sofa calling now!