Time to see a Dentist! All you can maybe do is get a temp. fix for now but you do want to get that looked at before it gets worse and it costs more to take care of it. Do it soon! I waited too long and it cost me about $5000.00 for crowns and a bridge. Don't let it go for much longer!
Hmm... I went to dental assisting school and worked chairside for many years, but you'd need a dentist to diagnose this. I can make a few suggestions as to what it might be, though.
I can't tell based on what you said if you're talking about one tooth or your full arch. Pain in one tooth that only appears (or gets much worse) when biting is usually the result of a cracked tooth. The only fix is a crown, if this is it.
If you're talking about both sides of your mouth hurting, the next big question is: How's your oral health? Do you think you might have a lot of cavities? If you're usually spot on with your dental care, my money would be on tooth grinding or sinus pressure. If you clench your teeth when you're upset or grind at night, you'll usually get jaw pain, not tooth pain, but it presents itself differently for different people. You can also grind down your teeth so much that they'd need crowns and/or fillings. If you suspect this is the case, you need a night guard, so you'll stop damaging your teeth/ jaws, and then you'd have to go about restoring the individual teeth. Sinus pain, on the other hand, is super easy to check. If you've been sick or have allergies, your sinuses fill up. If you have especially long tooth roots, they can press on the sinus cavities or vice versa. I actually have this problem. All of my upper teeth hurt every time I get sick and it lasts for a week or so. If you think this might be it, bend over and touch your toes. If your teeth hurt worse while you're touching your toes, it's probably your sinuses. An OTC decongestant, like Sudafed should help.
Aside from this, there are a lot of other reasons why a tooth would hurt and sometimes teeth even refer pain to other areas of the mouth, so it's really hard to guess what it might be, and the way to treat it will vary based on what's causing the pain. I gave you a few ideas on what it might be and what the treatment for each is, but I'm no dentist and even if I was, I couldn't diagnose without x-rays and an exam. Good luck. If you do visit a dentist, please let us know how it goes.