It really depends on your diet whether you need to supplement salt or not, especially for rides under two hours. If you're eating salty snacks and/or salting your regular food, you may not need extra sodium supplements in your drinks. You can do the old trick of weighing yourself nude before and after a ride - that will give you an idea of how much water you've lost via sweat - and then figure that you've lost 500 to 1000 mg sodium in each liter of sweat. That varies from person to person, and for any individual, it varies depending on how well acclimated we are to the heat - conserving sodium in sweat, while sweating more heavily, is one of the ways we acclimate.

If Gatorade tastes salty to you, it could be your body telling you your sodium level is okay. Heat stress by itself can cause a headache even without dehydration. When the weather's this hot, you can freeze your bottles ahead of time and have cold water for at least the first 45 minutes or so of a ride, which really helps cool your body. Try just plain water and see whether that helps.

Congrats on your milestone!