1997 Other Nissan Models Rattling and Clicking while acceler

For the past two days my Nissan Pickup has been making rattling and popping noises while I accelerated. I can't be sure if it is near the front or back of the engine block though. At first it was nothing other than just that. But then I started it one day and my entire truck started jerking as the RPM fell below 1000, down close to around 500-400 and then jumping back up to 1250-1300. Once I gassed it, it stopped, but it had never done that before. Also, just earlier today I was driving down the road and stopped at a red light. As I was stopped (First gear, clutch all the way down) It rattled, the RPM dropped and then it just died as if I had killed it by picking the clutch up without gassing. After that I tried to restart it, and while it was turning over, it was doing it like it was a huge effort. I just changed the battery 4 months ago, so I know that it is still good. Anyways, after I turned it off completely for about 15 minutes, I tried again and it started. I got it home alright, but the noises started up every time I had to gass to keep at speed. (For example, my 3rd gear goes from around 22mph-40mph and the rattling starts around 30 mph)

Can anyone help me with this?