Takes naps. I'm also in my 2nd trimester, 2nd pregnancy, and battling the same thing. I'm attributing it to the fact that I have a toddler to chase after when I get home from my full-time job, plus cook dinner, plus do laundry, plus clean up the house.
I have found that if I can take a nap during my lunch, although I'm not sure if you work or not, I do much better in the afternoons and evenings. I drive to a park close to my job, set my portable alarm clock, sit back in my car and close my eyes. Works wonders!
Also, remember that your 2nd trimester has really just started so it might be another week or so before the symptoms go away. In any case, rest as much as you can. Sometimes, just sitting down for a few minutes in a quiet place an closing your eyes works well, too. Don't try too hard to not be tired. That will only make it worse!