10km and headache

I am up to 10kms about once a week but what I haven't figured out is the nutrition/water part of it for running that distance in the heat while still breastfeeding. Wow Saturday was hot and humid and I ran 10 at 8:30am only to have a headache for the entire day. Not cool with a teething sad 4 1/2 month old...and husband working all day. I need to get a grip on this because it's been a hot summer before and I know that I do not do well in the heat. I am really really happy with my ability so for. I am impressing myself to already be doing easy 10kms. Hoping to do some doubles in a day to increase mileage. I got all my eload and hammers out from pre pregnancy so I am going to start trying them out during runs to see how I feel.