What Causes Persistent Headache, Exhaustion, Fatigue, Dizziness And Lack Of Energy?

hello :) I live in Northern/Central vt am a 43 yr old woman.. my 19 yr old daughter and I have been experiencing odd symptoms, for three plus days.. headache, exhaustion, fatigue, no energy, dizziness, strange head, like theres a cloud in your head and you cant think.. we are hungry and thirsty though... symptoms began with extreme heat at beginning of the week.. and a sense of desperation which i attributed to the heat and humidity (90 s) and our small apartment, which is poorly ventilated. We did swim in the lake (Champlain) which was closed yest. due to blue-green algae..I feel slightly better out of apartment, which I thought maybe was carbon monoxide poisoning (old heater) and fresh air helps me but she feels just as badly irregardless of where she is..