What Causes Weakness And Body Pain After Exercising?

I worked out last night. The first night in maybe a week or so. I woke up today feeling fine. I had lunch and a few hours later i had a meeting to go too. It was in a very warm room an immediately i took my sweatshirt off. I was in the room for about 1 hour. After about 35 mins i started to feel weak. My body started to ache and i was getting hotter by the minute. Now (about 2 hours later) i still feel very weak an im still pretty warm. Anything i can do to help get me back to feeling 100%