Welcome to BYC. Glad you decided to join our flock. I assume based on your reference to a heat lamp, it is real cold where you are. Double Laced has given you some good advice regarding light. Other reasons that hens can stop laying besides shortage of light is stress (created by a move or from predators in the area, etc.), improper nutrition, broodiness, molting, age, disease, and internal injury. Please feel free to ask any questions you may have. We are here to help in any way we can. What kind of chooks do you have?
X2 You don't need heat. Lots of reasons why chickens can stop laying from molting, worms, some sort of illness, stress, injuries, they could be eating the eggs or something else is eating them, they may be laying them in some secret nest, etc...Stop by this thread about why my chickens aren't laying and maybe you can glean some info on why yours have stopped. You can even ask questions here too....https://www.backyardchickens.com/t/423023/why-arent-my-chickens-laying-here-are-your-answers
Good luck and I hope you can figure this out soon!