what is my problem? isuzu mu 1991 turbo diesel?

i was approx 10kms from home when i stopped at a give way sign and was consumed by white smoke, i stopped the 4x4 and checked all the fluid levels, oil was low, so i topped it up and drove home, i noticed a drop in power and just got home before it died. then a few days later i drove about 400metres down the road, as soon as i hit a small rise in the road it started to struggle and then the smoke appeared again and it died, i managed to get it going again but it died another 2 times on the way home. a few weeks later it will still start and idle but when i try to drive it starts to struggle like it is not getting enough diesel, pumping the diesel filter pump brings the idle back to normal, but driving is no longer possible.