Hi Cake,
I started wearing make-up about a year ago (I seemed to get bad spots when I developed RSD so had to use it) and I always had the same issues as you with most foundations. One of my mums friends recommended a mineral foundation by MAC though and it works really well. It's in a small tub and it goes on like a powder so it doesn't make your face as sweaty/greasy and stays on well when you get really hot. It's a little bit expensiver then some of the liquid foundations but it works well for me (and my mum also).
I hope you find something that works and get to feeling better soon!
Alison.