My oldest son has similar issues. I got him a Green tea mattress and a water proof hypoallergetic breathable vinyl free cover and high count cotton sheets because he feared he'd ruin the bed with his night sweats. He really thinks the mattress cover made a great difference and he doesn't get so hot now. I thought it would make it hotter, honestly, He's a side sleeper and says it feels much better on that bed.

I think it also helps to have cooler sheets... really old cotton sheets are my favorite for wicking off heat in the hot summer. You can absolutely feel how great they are if you find them at a flea market, yard sale or thrift store. They feel softer and silkier than most modern cotton.