My whole first bottle I always got stuffed up. I take it in the am only now and I cut my dose down to 7.5mg. Seems to help a lot. Even at 6mg a day, erections are really strong. I have also switched and done 7.5 EOD and still very good results. I prefer every day but EOD is adequate.

Never experienced headaches from it. Make sure your water intake is good. That alone (although unrelated) always gives me headaches.