Please help me with my car!?

Ive been posting questions about my car, but the condition has worsened so I may have enough deatails for you guys to get an idea of whats going on. it started off sputtering a bit when i accelerated, and then progressed to a full rumble, almost like a chopper, or a high velocity clicking (surging?). The car jerks/bumps back and forth as i accelerate. sometimes it wont accelerate at all, stuck on a single low speed like 10 or 20 and i have to fight with it, pressing on my gas, letting off my gas, to make it go (very slow and stressful process) . When im stopped, it now will continue to bump around, sometimes small frequent bumps, sometimes harsh ones like someone hit my car or something. Its like theres rocks tumbling around in there! this is really hard to explain but im doing my best. also, it is not leaking oil but im burning through about a quart a week, maybe more. Please give me some ideas as to what this could be, and please tell me about how much it would cost to get it fixed. I would really really appreciate some experienced help here. oh btw its a '99 ford escort with 130,000 miles. Thanks!!