Why am I experiencing severe tooth pain in teeth, especially in all bottom teeth?

Probably No Cavity. If truly all your bottom teeth hurt, it's probably not cavities or infection. More likely is generalized gum recession, exposing your tooth roots, which can be very sensitive. Another likelihood is clenching/grinding your teeth (at night?), which places a lot of stress on them and can make them sensitive. Only a dentist can tell you for sure. Sounds like you could use a thorough check-up.
Vague. There are many causes of tooth pain- cavities, new fillings, grinding/clenching, gum problems, nerve issues with the tooth and/or infection, etc. If a tooth is infected, the infection can spread beyond the roots and into the underlying gum tissue and bone, which does become a concern. See a dentist.
ASAP see Dentist. Please see a dentist to help you resolve the issue which is causing you pain. Waiting will cost you money and more pain. Make an appointment asap please.
Get checked asap. Tooth pain can be very stressful and can happen for a variety of reasons like cavities going towards the nerve, infections, tooth absess, broken and cracked teeth. A dentist can quickly figure out the reason for the pain so go ahead and make that appointment.